As my parents have always stated to my siblings and myself, " I don't care if you don't like each other. In fact, I don't expect you to always like each other. I do, however, expect you to act like you like each other, so long as you all live in my house."
The forums have an ignore function. If you don't like reading what someone is posting, ignore them. If they are crossing the line into harassment, report them. Same concepts can be used in game.