I'm sorry you feel that way. I know what you mean. It can just wear on you. I find that there are some secrets to try and avoid feeling that way.
Always state your opinion from what you understand, and your experience and then it does not matter what people say after that right? Personally, I will sometimes comment when i know it is not a popular position, but I make sure I believe it, and I am willing to let others persuade me if they want. With that attitude, nothing people write bothers me.
Don't get into things with harsh feelings. Sometimes it feels nice to say something about someone else that has posted ideas which we feel are just dumb. Make sure the comment does not come across as negative or someone is going to be on the defensive. Then who knows what happens.
Remember, this is the internet, it is not life. There are definitely some weirdos around, and we really can't expect too much from a free online forum. It's sad but too true. The good thing is that we don't need an online forum deciding how we are going to feel. We get to choose that ourselves, no matter what is going on in our lives.
On a lighter note, there is a lot of good stuff here too. We just gotta help where we can and learn where we can and let the rest fade away into the background.
Cheers!