How to deal with people who bring you down?

I was wondering how to deal with people who bring you down after an argument or a disagreement? I just recently got into an argument with somebody over the internet and I know with the internet you can just zone out or not pay attention but it's those small things that really get to me. Of course on facebook people talk with terms like "Awez" or "Ily" or things like that. This certain person decided to say something along the lines of "Do you know how ******* annoying that is? I mean seriously were not in animefun land ok so please you guys just grow up" me trying to resown I told him to just calm down it's just facebook if we have a problem we can just try to tell the person who's annoying you personally that you dislike it. Of course then other people came in and said "Oh well you know it's facebook and all" And then he tried to be sarcastic... Long story short we got into an argument about these things, and he was just pulling big words out of no ware, acting like I'm his lesser... The conversation kind of spiraled out of control, and every single chance he had to prove me wronge in that argument he did, trying to win the affection of the others who were involved in the conversation. I sware he was just being so stubborn with me, any point I tried to make, he just shot it down acting as if I have no points or values to offer... In the end he just made some big statement about how I'm wrong and I need to listen to what he said about things and I just stopped with it all. I realized immediately after though I was feeling more down, not really up to do anything, sadder... I didn't know why, or how he got to me, but weather I thought I was right or wronge, it just kept bugging at me... I was wondering if anybody knows how to prevent this from happening... I mean I even apologized and he just kept going on... It just brings me down.. Thanks.