There's not much new here to advance the "whether waterboarding is evil" debate. The "pagan" angle -- the claim that those who advocate torture argue from a position of pagan virtues, instead of Christian virtues -- requires those who advocate waterboarding to agree that waterboarding is torture, which Thiessen at least does not.
Thiessen's "radical pacifist" angle, meanwhile, confused me a bit at first; he didn't just say opposition to waterboarding comes from a position like radical pacifism, but one that it "effectively" is radical pacifism. I think now he was saying that the effects of both are the same -- viz, "the death of thousands."
Since, however, he agrees with everything in this Ramesh Ponnuru post, then he agrees that, "There is some rule he [Thiessen] wouldn't break though the heavens fall."
If this is the case, though, the "radical pacifist" charge amounts to little more than an observation that circumstances have not yet brought him to the brink of the line he himself won't cross -- circumstances in which he too would be "effectively arguing from a position of radical pacifism."
To my mind, introducing the term "radical pacifism" clouds rather than clarifies the discussion. As a matter of rhetoric, though, it leads up to Thiessen's assertion (in his first post) that "we [shouldn't] put pacifists in charge of decisions on war and peace. Same should go for decisions when it comes to interrogation."
Why shouldn't we put people who oppose waterboarding in all circumstances in charge of decisions when it comes to interrogation? Because it will cost innocent lives. What will happen, though, if people who follow Thiessen's own "though the heavens fall" rules are in charge of interrogation decisions when innocent lives will be lost if the rules aren't broken? Innocent lives will be lost.
Are we then to keep swapping out increasingly lax decision-makers as the circumstances become more dire?
If Thiessen wants to argue that his own rules are better than the rules of others, he can, but the inductive claim he offers in these posts is also an argument that his own rules are worse than are less rigorous rules.