To the OP...

There are three taboo topics not to discuss freely with acquaintances or strangers: Religion, sex, politics

I avoid talking politics with anyone, period. It's the quickest way to lose friends. Occasionally, the topic will be brought up among my closest friends and we are careful of what we say, but we generally agree with one another and are comfortable enough to express our views without getting upset, even though between us we are split down the middle of political views. I had one friend who was a bit of highly opinionated so-and-so, but we managed to agree to disagree. It's definitely not easy, and I feel what you are feeling romanticrose, I've been in that situation and it definitely hurts. I'd ditch that friend right away if he's going to bully you making you feel bad about what you believe in.