A lot of the teachers I used to work with not only knew about my former hobby, they'd seen my site. I think if the principal had seen it, I'd still be working there.
What people do in their personal lives is...well, personal. As long as it is nothing involving harm to kids, they should fuhgeddaboudit and worry about their OWN lives for a change.
This is akin to someone like me taking offense because a teacher to my kids is a Christian or something.