As a "stealth" trans person, I have had a number of opportunities to educate ignorant cis people about trans issues, and I have usually taken those opportunities. The thing is, a lot of ignorant people won't listen to someone from the group they hate, but they WILL listen, at least for a little while, to someone they think doesn't belong to the target group. Since people don't read me as trans, they let me weigh in. If they're actual bigots, they won't listen. If they're simply ignorant, they often will. And, as a professor, I actually have the authority and the gravitas to shush a student every once in a while and say, "No, let me finish. You had your say; now let me have mine." I am not shy about it.
With cis people I have talked to, the bathroom issue has come up only twice that I remember, but I have made my views known on both occasions. If those folks had pegged me as trans, they probably would not have given me any consideration. But because they see me as cis, they listen. I have also talked with cis people about other trans issues without their knowing I was trans.
Actually, it kind of burns me up that some super-activist trans people tell me that because I am not openly trans, I am not doing anything for the cause. I volunteer here, I have contributed here, I have contributed to the TLC, I have educated colleagues, I have educated a couple of doctors, I have supported specific trans people I know (sometimes monetarily), I offer my trans students a safe and respectful space--it is even in my syllabus. I also talk to cis people as one of them, and they listen BECAUSE they think I'm one of them.
But trans activists tell me I do nothing. Well, sometimes I can do what they can't.
This really came out as a rant, didn't it? Well, it's not any less true for all that.