On the subject, I give you an excerpt from A.C. Ewing that I personally found illuminating. Concluding that "We may ... regard punishment as a kind of language intended to express moral disapproval" (paralleling my argument that criticism is the "punishment of first resort"), he writes:
To punish a lesser crime more severely than a greater would be either to suggest to men's minds that the former was worse when it was not, or, if they could not accept this, to bring the penal law in some degree into discredit or ridicule. One of the requirements of a good moral code is that there should be a right proportion between values, and, in so far as penal laws affect popular morality, they ought to help and not hinder right judgment in this matter. This is not to fall back on the old retributive conception that a certain amount of pain intrinsically fits a certain degree of moral badness. [M]oral condemnation of [murders] can only be suitably expressed by inflicting a severer punishment for them than for [thefts]; but this would not be an objection to lowering the penalty for both, because there is no necessarily fixed scale that we can see by which so much guilt deserves so much pain. There is another bad effect of disproportionate punishments. [I]f a man is very severely punished for a comparatively slight offence, people will be liable to forget about his crime and think only of his sufferings, so that he appears to be a victim of cruel laws, and the whole process, instead of reaffirming the law and intensifying men's consciousness that the kind of act punished is wrong, will have the opposite effect of casting discredit on the law and making the action of the lawbreaker appear excusable or even almost heroic. These punishments are specially liable to produce an effect of this sort on their victim. He will be likely to think the penalty excessive in any case, and the great danger of punishment is that this will lead to self-pity and despair, or anger and bitterness, instead of repentance, but if he has really good grounds for complaint, this danger will be doubled.
A.C. Ewing, A Study of Punishment II: Punishment as Viewed by the Philosopher, 21 Canadian B. Rev. 102, 115-116 (1943).
This supplements quite well some of the points I made in the above post. First, that the justifiability of a given punishment is inherently relational to how we punish other offenders: it's not that there is an objective amount of "pain" we should give to thieves or murderers, it's simply that murderers should be punished more than thieves. The complaints of those who ask why Israel is "singled-out" for greater vitriol than, say, Burma or China, are based on a similar moral intuition: they don't necessarily object to raising the amount of criticism we direct to human rights violators across the board, they merely demand that the judgments actually correspond to a reasonable hierarchy of violation.
Second, I think it is very clear that the perception by Israel of being excessively punished is sparking a similar reaction to that predicted by Ewing: namely, "self-pity and despair, anger and bitterness". And there is a corresponding tendency amongst Israel's supporters to label even clearly wrongful acts by Israel as excusable or heroic because they are thumb in the eye of the groups engaging in over-criticism. One can see this dynamic in Palestine too, I think: excessive Israeli punishment (e.g., house demolitions for not getting building permits) leads many to see even clearly wrongful Palestinian acts as "excusable or even almost heroic".