At one level, this is a ridiculous assertion. It is quite easy to criticize Israel without even giving the whiff of anti-Semitism. Allow me to demonstrate:
The traffic in Tel Aviv is terrible, and the buses come way too infrequently to make up for it.Easy!
Of course, that type of criticism isn't exactly what the speakers have in mind. And I can play this game for awhile, with criticisms less mundane than traffic ails: "Israel should adopt civil marriage." "Israel should never have withdrawn from Gaza." "Putting settlements in the West Bank was a major strategic mistake." The point of the exercise is to demonstrate that no, not all criticism of Israel is out of bounds as "anti-Semitic." Particular criticisms phrased in particular ways in particular contexts are, or may be, and the way you figure it out is by looking into said particular criticism and assessing it individually.
And this is an important distinction, because it places the focus where it should be: on the particular criticism being leveled, not on a supposed massed Jewish communal psychopathy that claims anti-Semitism as a reflex. The latter position is of course anti-Semitic in of itself, as it takes as its premise that Jews regularly lie in pursuit of their political ambitions. And as David Hirsh notes, it's not altogether clear why it should matter even if it were true in an individual case -- the subjective motivations of the person claiming anti-Semitism only tangentially, if at all, impact whether the statement in question actually is anti-Semitic or not. Whether the claimant honestly believes what she is saying or is lying through her teeth, there's no reason not to go through the analysis. In reality, some criticisms of Israel are anti-Semitic and some are not, and the only way to distinguish between the two is to closely examine the individual criticism in question.
All that being said, I will cop to the following: There are critical positions about Israel, which touch on issues that are exceptionally important to matters of justice, equality, freedom, and other important social questions which require extensive debate and discussion, which are hard to present without them seeming anti-Semitic.
And that's a good thing.
Well let's approach it from the opposite angle. Why would it be a bad thing? The answer, it seems to be, is that it is generally unfair to be accused of anti-Semitism (or forwarding an anti-Semitic position, or being insufficiently attentive of anti-Semitism). There is a perceived entitlement of people to not have to deal with it unless the case is exceptionally egregious. Consider Joseph Levine's controversial article On Questioning the Jewish State. Levine claimed their was an inherent conflict between the concept of a "Jewish" and a "democratic" state. And he concluded by saying that at the very least, the question had to be discussed "openly on its merits, without the charge of anti-Semitism hovering in the background." This, to me, is a bizarre assertion, for the simple reason that whether or not a position is or is not anti-Semitic seems rather clearly to represent part of its "merits." To say "forget anti-Semitism -- is this a valid moral position or not" is nonsense. One would hope that the validity of a moral position depends quite significantly on whether it is or isn't anti-Semitic!
I honestly do not understand the foundation for this entitlement. Why is this something that people are owed? Why is there any right to be free from the vicinity of an anti-Semitism claim? At best, one could say that it stems from an obligation of presumed good faith -- we should not assume our interlocutors' positions stem from evil motives. There are three problems with this argument, though: (1) It's internally contradictory, since the objection to being called anti-Semitic inevitably takes the form of claiming the accuser made the charge in bad faith, (2) It isn't altogether clear why Jews should be forced to assume good faith of non-Jews with respect to matters of Jewish equality, given that historically such trust has not exactly been earned, and (3) It relies on a particular (and particularly narrow) conception of anti-Semitism wherein it only exists if it is the product of conscious and overt antipathy towards Jews. This definition of anti-Semitism is debatable at best, and in the context of the instant discussion seems to serve more as a way of shielding a wider-ranging discussion of the subject by transforming it from a systematic discussion of what Jews are owed as equal global citizens into an investigation of the personal character of the individual.
Consequently, I reject the notion that there is any special entitlement to not have anti-Semitism raised as an issue when Israel is discussed. Indeed, as the title of the post indicates, I consider it a qualitatively good thing. The existence of anti-Semitism limits and circumscribes what arguments and claims one can validly make against Jews. Claims against Jews are constrained by the rights Jews possess -- hopefully that isn't controversial -- and the history of oppression against Jews and the ensuing power dynamics Jews experience vis-a-vis gentiles have a significant impact on what those rights are vis-a-vis the non-Jewish majority. This doesn't mean that Jews are immune from criticism, of course; rather it means that the past and present nature of anti-Semitism is a significant input into the calculus that governs what sorts of criticism are valid or not.
Anti-Semitism is an extremely important facet of any discussion regarding Israel. Any discussion of Israel is a discussion, in part, about what Jews are at liberty to do, how the political institutions that govern them can justly be structured, the sort of self-determination they are entitled to, and the epistemic status of Jewish versus non-Jewish perceptions of Jewish behavior and moral claims, among other things. In all of these discussions, matters of anti-Semitism should affect our analysis considerably. These are not the only things that matter, of course, but they do matter, and if you talk about Israel without having these considerations foregrounded in your mind, you're talking about Israel poorly.
The norm whereby anti-Semitism is always at the forefront of discussion is good because it forces people to treat it with the requisite degree of seriousness in forming their policy positions (lest they be accused of anti-Semitism). When having discussions about Israel, we want to be sure that people (and particularly critics) are thinking really hard about anti-Semitism when formulating their opinions, and the prospect that one's position will be labeled "anti-Semitic" is an excellent motivator to do just that. A reasonable position on Israel will invariably require one to seriously grapple with the ways in which historical and present anti-Semitism implicate the positions that you hold and how your arguments account for the actual facts of Jewish existence and what they need to exercise their individual and collective rights as a people.
Consider as a parallel discussions about affirmative action, which also suffer from the oft-heard claim that "one should be able to oppose affirmative action without being 'racist.'" Now, I'm a strong supporter of affirmative action. Nonetheless, I recognize that there are important debates to be had about the propriety and legitimacy of affirmative action programs, and critical positions can be held by persons who have perfectly egalitarian views towards racial minorities. It is important to have these debates, and we should have these debates. But it would something else entirely to say that we could even have an intelligible, let alone productive, discussion about affirmative action without the issue of racism entering into the picture at all. Yet as with anti-Semitism, people seem to feel they have an entitlement to talk about affirmative action without having their particular position's compatibility with racial equality called into question. The "debate" they want to have about affirmative action -- one where one is not permitted to consider the impact and continuing salience of racism or assess the validity of particular positions against the metric of racial justice -- is no debate at all; it would be incomprehensible gibberish. Keeping "racism" at the forefront of affirmative action debates ensures that an important element of the conversation which people very much would rather ignore stays at the center of the analysis. That's a very good thing.
There is no right to forward a position regarding Israel and have people ignore how it impacts and is impacted by contemporary and historical anti-Semitism. The best way to not have a position called anti-Semitic is to take anti-Semitism seriously and take a hard look at how one's beliefs and positions are responsive to anti-Semitism's existence and salience. Engaging in that deep, searching analysis will undoubtedly weed out certain types of "criticisms" which cannot be reconciled with an opposition to anti-Semitism -- and that's a good thing. And by the same token, in my experience people who do that can take a variety of positions on Israel without being called anti-Semitic -- and that's a good thing too.