It's all about how you react to it. The best thing to do for negativity is just ignore it, tell yourself "It's just a forum and not worth my stress." If a thread gets rude, don't go back to that thread. If someone stalks you and posts negative things in reply to your posts, block that person.
People have all kinds of inner issues that cause them be rude, and none of those issues are related to you, so don't take things personally. And remember you're dealing with a bunch of pot heads. When we're high, we're happy, and when we're sober, we really don't want to be.
Sometimes you'll cause them to be rude by being stupid. For example, yesterday I made some people less than happy by saying we won't go extinct by killing all the bees. The whole thread cracked me up and still makes me laugh, but when I knew I'd posted something that would make them mad, I just didn't go back. The truth is I know nothing about bees, haha. Give them a hard time, laugh about it, and move on. Sometimes this is what they're doing to you, too. Nothing on here is worth your stress.