Either allow nothing at all, or don't allow anything that creates or encourages active disruption. Selective approval of non-disruptive message? BAD IDEA.

A passive statement about not hating people is hardly disruptive. Good for the student.

Uh, OK. If I were this guy's wife I think I'd be a bit worried. Just sayin'.

Personally I think schools ought to be able to ban any expressions that might be too politically charged, because the school setting isn't necessarily the best place for that. The political emotions could be a distraction (not the gay sex fantasizing that this principal is apparently concerned about.) But of course, if the schools prohibit an expression of one type, they have to be consistent. I think that the school board ought to set the policy and have a clear method for students and parents to petition if they think that a particular expression is causing problems and needs to be added to the 'no' list, or to petition if they wish to have something permitted that has previously been banned. As long as the community is allowed to make the decisions based on what's best for the educational environment, then you won't have one person in authority acting according to his or her own biases to prohibit certain expressions but not others.