how do you change your emotions from "oh fuck everybody hates me, better prove them right" to something else?
Do you want good advice or bad? There are several ways to go about this.
The bad advice: Hope Stockholm syndrome kicks in. You are captive in the stares and hate of the forum but eventually you grow to love those that hate you!
The better advice: However your problem is you are reacting to negativity with negativity and you wish to change this. If you keep proving them right this becomes a looped circle of you proving someone right making them hate you more making you prove them right again.
In order to cut this circle you can. Stop doing things that would make anyone hate you (in other words care about what they think about you) this methods results in changing you and your actions.
Or you can ignore the fact they hate you resulting in not making anyone hate you more than the base level. This means you don’t change how you act you just don’t care that they dislike what you said and thus you don’t react to them disliking you.
The final method is simply a different version of the first one. Where you care about the other people resulting in you not wanting to annoy them. This is the love everyone method that I employ.
The thing to remember is you can’t please everyone and you shouldn’t you don’t have to agree with everyone but you can argue in ways that are less blunt and offensive while still getting your point across.
Now how to change the emotions to suit this... Jeez you didn’t ask an easy question did you. Assuming you want to change which is why you asked the question use any emotional input you can. Maybe the only thing you like about the person is there avatar, use that to try and shape how you feel about the person and use that to respond in a pleasant way.