If you want to defeat the enemy (e.g., the Iranian regime), it seems to me you should:
1. Know Your Enemy: The more you learn about him, the better you'll be at figuring out his tactical and strategic weaknesses, and those of people like him.
2. Help Friends Know He's Their Enemy: Often, some of your fellow citizens don't grasp how bad your enemy is. If you can get him to indict himself in front of them, they may learn.
3. Know Your Enemy's Friends: Some others among your fellow citizens might underestimate your enemy's dangerousness, because they're unaware of how many people support him. The applause for Ahmadinejad at Columbia, which some have pointed to as evidence of Columbia's error in inviting him, strikes me as quite valuable -- it shows that even in the U.S., Ahmadinejad has supporters, which helps show how dangerous he and his people really are.
Of course, there is a countervailing factor:
4. Avoiding Giving Your Enemy a Chance To Make More Friends: It would be good to avoid giving Ahmadinejad free propaganda opportunities, through which he could mouth friendly-seeming banalities. But it seems to me that the Columbia's World Leaders Forum is in general not a great propaganda outlet -- and this is especially so when President Lee Bollinger asks questions that help show Ahmadinejad's true nature.
So here, even more than in most situations, it seems to me that the interests of giving students more information coincide with the national interest. A commenter to my earlier post writes, "Ahmadinejad is our blood enemy. He should be defeated or, optimally, killed. We waste time that would be better spent accomplishing one or the other by listening to him." I don't think it's either-or -- I think that listening to people like Ahmadinejad, especially in forums such as the Columbia forum, will indeed help us defeat them (and, where helpful and appropriate, kill them).