Noban, if you do get a chance to communicate with the teacher, and you don't mind REALLY being the bad guy, tell her you got some advice from a middle-school teacher you know in Illinois:
It is NOT your job to tell your daughter that her opinions on these issues have to be "toned down" for the classroom. The teacher has every right to ask that your daughter stay on topic, but it's HER job to ask it.
Moreover, if she brings up the topic of gun control, she has NO excuse for singling out any student to deride his/her opinion. If she doesn't squash the kids who pipe up FOR gun control, in other words, you have cause for a serious complaint here.
It's disgusting that she would feel the need to call home and ask your ex-wife to alter her views (and yours) so that your child wouldn't learn them! It doesn't matter what she thought of those views.
A few days ago, a child used the "n-word" in my class. I informed him that he was free to say whatever his parents would allow him to get away with at home, but that I wouldn't accept that speech here. That was the end of it. If he does it again and I have to call his parents about it, it'll only be to make them aware of the situation--and if they inform me that they think that's fine and dandy for him to say, that's their business. I only have the right to ask him to refrain from certain speech in the classroom, and even then there must be an overriding reason for it to be considered ethical. Avoiding any stamp of legitimacy on racial insults is such a reason; political disagreements are not.
Kids absorb more than you think