The big area of controversy is to what extent liberal domestic policies are necessary to waging the war on terror. Paul is dismissive of the idea:
Beinart's heavy reliance of the role of the civil rights movement in the Cold War seems misplaced. Similarly, the arguments made by his fellow pro-defense liberal Martin Frost are unpersuasive. Frost argues that our efforts to promote democracy abroad are being undermined by the alleged mistreatment of detainees and supposed civil liberties abuses in the U.S. Frost offers no evidence for this proposition, and a moment's reflection is enough to conclude that it is entirely implausible. Surely Frost does not believe that the terrorists in Iraq are trying to bring down the democratically elected government because of the interrogation techniques at Gitmo. Or that the Saudi government is resisting democratic reforms due to the NSA electronic intercept program. People in other countries favor or disfavor democracy based on their perception of their own interests, not their perception of the U.S.
The argument obviously fails if it's a pure X --> Y causal relationship. But I sincerely doubt anyone is making that argument. The right question to ask is whether American human rights abuses are pushing Arab citizens away from supporting Western-style democracy. That seems altogether plausible. Indeed, the argument works under Paul's own metric of individual interests.
Imagine an average Arab male, just liberated from an oppressive Ba'athist regime. After years of living in fear of an all-powerful and unaccountable state, what is one of the biggest draws of American democracy? Put bluntly, it's the promise that in America he won't be dragged off to an isolated prison for no apparent reason, without any sort of trial, procedures, or chance to clear his name, and subjected to torture. When the promise is put on shaky ground, America loses one of its greatest advantages. And remember, it's a perception issue--all jihadists have to do is cast doubt that America-the-ideal is America-the-reality. Place a picture of the Statue of Liberty next to a picture of Abu Gharib, and that point comes off rather potently. This isn't to say that democracy has no other advantages outside of the "won't-get-dragged-off-and-shot" variety, only that this is a major one and we sacrifice it at our own peril.
Contrary to Mr. Mirengoff's insinuations, there is historical precedent for this. One of the key motivators behind the landmark Brown v. Board decision was the Justice Department intervening, for the first time, on the NAACP's side in a segregation case. Why did they do that? Well, as Derrick Bell has convincingly argued, they did it because the State Department kept on receiving cables from its diplomats screaming that they were getting mauled in the 3rd world over Jim Crow. We could not simultanously preserve such a blantant apartheid system and still claim to be defending liberty and equality on a global scale. I think that argument still applies, and the political party most able to transmit a persuasive pro-democracy message abroad will be the one that shows the greatest commitment to it at home.
What Paul is really steamed about, I think, is the implication that Republicans are ill-suited to win the war on terror. He thinks this charge is most unfair, and what's more, he thinks that few Democrats really take terror as seriously as Beinart does. I'm certainly in no position to respond--after all, I echoed Beinart's claim over a year before the book came out. But I'll merely add two things.
1) This argument is a mirror image of the Rovian assualt Republican's have made on Democrats since 9/12/01. Turn about is fair play.
2) Taking Kevin Drum as my guide (and I think he's a pretty good bellweather for the Democratic mainstream), the primary reaction to Beinart's argument hasn't been to decry its militarism, its been almost along the lines of "duh, that's what we've been saying for years". As Drum writes:
I think he could give the keynote address at YearlyKos and not really say much of anything the audience would disagree with. If Beinart really is the standard bearer for a new incarnation of liberal hawkishness, then we're almost all liberal hawks now.
So if Paul thinks Beinart is mostly on target, and most Democrats also think that Beinart is on target, then I think that's pretty compelling bipartisan support for the mainstream Democratic position on anti-terror policy.
UPDATE: My latest reply to Mr. Mirengoff is here.