Lots of ways to do that:
1. Do not open any thread. No threads - no posts you do not like.
2. Become a moderator and kick thoses bastards out.
3. Create your own forum and invite only people you like.
4. Pay forum owners to add a feature.
5. Change yourself. Some groups of people think there are to much hatred around them. In fact, nobody gives a **** what they are doing.