I agree with the basic argument that Alexander is a savvy SOB and knew what he was in for...

BUT, you're making it sound like getting heckled on stage was desirable. I don't agree. I think it is more appropriate to say that the NSA is between a rock and a hard place. They could either...

* Get heckled and look culpable, but maintain the illusion that they give a shit what the general public thinks, or...

* Not attend and completely look like assholes hell bent on violating civil liberties.

Keith Alexander didn't win any friends by getting heckled. He just made fewer enemies.