If you can't say what you want in one forum, you're free to express yourself anywhere else on the web. The most free place you can ge to express yourself is on a blog on your own server. But even then you will sometimes be restrained by your government.
Every forum on the net is an interest group. Where people discuss a limited set of interests in limited manners. The scope varies widely, but there are limits.
The goal of any forum is to help its members feel welcome, resolve issues and have fun.
People who want to argue just for the sake of arguing are known as trolls. They can not be shut up by arguing with them, this is called feeding the troll, arguing with a troll keeps it alive.
There are three ways to get rid of a troll.
1) Be 100% nice and objective, if the troll discovers it can't make you angry it will eventually leave.
2) Ignore the troll, with no responces the troll gets bored and leaves.
3) Ban the troll.
Here's a nice video about dealing with poisinous people in a community.
YouTube - How Open Source Projects Survive Poisonous People (And...
Also, check out this book (it's even free, if you like readong on a computer screen)
Art Of Community Online♥|♥The Book On Community Management, by Jono Bacon