From his speech today:
An ill conceived meeting between the President of the United States and the President of Iran, and the massive world media coverage it would attract, would increase the prestige of an implacable foe of the United States, and reinforce his confidence that Iran's dedication to acquiring nuclear weapons, supporting terrorists and destroying the State of Israel had succeeded in winning concessions from the most powerful nation on earth. And he is unlikely to abandon the dangerous ambitions that will have given him a prominent role on the world stage.
A meeting is itself a concession? And diplomacy is about prestige? Look: any "ill-conceived" meeting with any foreign leader is a bad idea. But a president should be open to anything that might advance the interests of the United States and its allies.
Ruling out any top-level face-to-face dialogue in advance as a blanket ban seems foolishly rigid to me. And it also seems to me that Ahmadinejad has scored some p.r. victories among those populations that the US needs to win over by appearing to be more open to dialogue than the US. McCain is right to put Iran's power in perspective. It's no super-power. But he's wrong to treat diplomacy as a form of theater alone. Many presidents met with Soviet leaders, including Republican presidents.
We need to maintain maximal vigilance with respect to Tehran. But we should also not be afraid or forced into an isolated crouch. I'd say Obama is winning this early skirmish in the campaign.