No people cuss at me and stuff. Not on this site, ROBLOX and all those other sites, one time I was roleplaying on Twitch and I thought my friend was roleplaying with me, HE CUSSED ME OUT.
This is the internet, friend. "Cussing out" is actually relatively light, to what some people on here are capable of.
In fact, it's pretty much not even notable, compared to what some people on here are capable of.
I don't think running is the answer though; that is an admission of defeat. Whoever advocates backing down, probably hasn't grasped the concept of human nature.
I find humoring people like that is the best way... show them that their words really are just digital text on a digital page.
"HEY TIMETORP YOU FUCKING G*Y MOTHER FUCKING N****R F*****T GET THE FUCK OUT OF MY RP!!!!! >:("
"Wow buddy, is this because I fucked your mum?"
"FUCK YOU YOU FUCKING C**T NO ONE FUCKING LIKES YOU WHY DONT YOU LEAVE"
"I could, but I'd rather join your CAPS PARTY, EVERYBODY NOW, CAPS, CAPS, CAPS, CAPS, CAPPING ALIVE, CAPPING ALIVE, CAPS, CAPS..."
So on, so forth. Don't run. Don't encourage and entrench their behavior. Just stand firm, but not in a confrontational way. Be indifferent, understand that you have the same protection as they pretty much: you're both behind a screen, probably miles away from each other, and everything is inconsequential. Just don't start using racist terms in some kind of counter attack, or you'll lose street cred // invite community-wide condemnation. I've seen that happen a few times. Best to keep the language moderate, and just shoot them with fluff.
Try not to apply offline socializing practices to those online, it doesn't work.
You need any more pointers, come find me, I'm usually bumbling around here once a day.