It's professional boundaries isn't it? Most teachers understand them but there's always some who don't. In some schools there's often a small group of younger activist teachers involved with SLT behaving as our politicians have done until recently - a mix of clueless and scared of being called bigots.
What does worry me are the teachers involved in LGBT etc groups. What are they thinking? The school's role is not to actively involve children in LGBT groups any more than it is to run groups to discuss heterosexuality!
From what I've seen the groups lack a structure, curriculum, are usually mixed age with older students sometimes running sessions and frankly are opening up both teachers and older students to potential charges of grooming.