While I usually agree with you NewChapter, I don't think this is an instance of those christian kids being close minded and in the wrong. I am perfectly capable of listening to views that contradict and even condemn atheism, but that doesn't mean that I am required to do so under every circumstance. It's not that savage's views are wrong or shouldn't be said, or that he was being a bully, it's that that speech to that audience was in poor taste given that his audience came to support him.
Let's use the example I used above about maybe a conference to bolster support for science education and keeping religion out of the class room. If I went to a talk that was supposed to be about how important it is that good science is used in the classroom and that kids get a good math and science education, and the speaker is a known evengelical pastor, but one that supports the teaching of evolution and doesn't think that creation accounts or ID should be taught in any self respecting class room. Let's say I go to this talk that is supposed to be supporting this idea of science education, and instead he spends his talk complaining about how the New Athiest movement has been terrible for science, and people like Richard Dawkins and Jerry Coyne have done far more damage to science than good, and athiesm brought about Hitler and Mao you know! Would I be obliged to sit and listen to that talk just to show that I am capable of doing so? I would probably shake my head, think "this is neither the time nor the place" and then leave. I think those kids walking out was the most peaceful and mature way to send the message that "hey, we know you're an athiest, but this is about gay rights, ok? This is not the time or place." Some of those kids might be close minded and left because they can't handle criticism, but it's also likely that many of them engage in civil discussion and debates with atheists and muslims and bahai about religion and god and spirituality and are more than capable of listening to criticism, but felt cheated by the bait and switch. Remember, they were there to support LGBT rights.
It's easy to condemn others when you support the message being delivered, but objectively this was just a bad move. I think Dan Savage is great, and I support LGBT, but I can't condone this as being useful to the movement or condemn those teenagers for leaving.