He didn't single out Christians? He singled out "the bible guys" who left PEACEABLY. Don't be coy.
He said "People often point out that they can't help with the anti-gay bullying because it says.....". He didn't say Christians. It's very clear he is referencing those people who bully gays and their use of literally interpreting those parts of the Bible.
So this leaves out people, even those who are Christians, that do not bully gays. It also leaves out those who take the Bible literally. Which was apparently the majority of his audience. That most likely includes the students who walk out as well.
He didn't identify anyone in the audience. If anything, the people who stood up and walked out identified themselves.
I don't think those students even did that, however. Because I'll say it again. It was a very small number of students from one school who walked out. Once again, did they leave because they were offended or did the teacher start that little exodus? Given how quickly they walked out either there was some part of the speech earlier that no one is posting where he was slamming them specifically or they felt that they were being targeted, which no one anywhere is saying there was, or even the mere mention of the Bible and referring to any part of it as BS was enough for them to leave.
For those who want to assume that even mentioning the Bible means them than it's their problem. If they want to assume that specifically referencing those who bully gays means Christians than it's their problem. Let's keep the focus on what he actually said. Not on what people wish to imply he said. Is criticizing those who use literal interpretations of the Bible to bully homosexuals in itself bullying? If so the implication to me is that any criticism of the Bible or those who use it to do harm to others is in itself bullying and off limits. It stifles any discussion.