I don't think they should, but I think they should be allowed to. You're never going to stop crazy people from saying crazy things, and sometimes those people might just happen to be teachers. Besides, if crazy ideas were verboten in education we'd still be in the dark ages slinging arrows at each other. Tenure was actually explicitly created for respected teachers to be able to say crazy things without getting fired. What are you going to do when a tenured professor starts teaching your child something you disagree with? Are you going to go with the same heavy-handed approach?

If you have a problem with the way your child is taught, bring it up with the teacher. Bring it up with the principal. Bring it up with the school board. Ask your child to be moved to a different class/section. Ask your child to be re-zoned. Or, all else failing, teach your own child. Maybe you should be more concerned about hiring standards for our teachers, or maybe consistent accreditation.