Under Texas state law, a teacher can be disqualified for being openly homosexual under a pact of 'morality.' I'm sure the Supreme Court has overruled this legislation, but you get my point. Conservative parents do complain about gay or questionable teachers. It's happened before. Luckily my admins are fairly liberal on this subject.
How does advocating the legalization of a harmless substance in any way impede on my relationship with students? I don't bring up my political opinion about anything in class. My students constantly try to get me to say who I voted for, my opinion about abortion, and yes, if I believe weed should be legal. I always defer or refuse to answer any of these questions.
I don't even add students on Facebook until after they graduate. In fact, my FB is pretty exclusive, which is why I laughed most of the time in conference. This parent pretty much stalked me.