If someone insults/bullies you online, it's called cyberbullying. This is something that can really hurt peoples feelings (so, I wouldn't consider doing it). There are a few ways to get rid of them...
Tell them, no one can judge you. You are who you are. No one can change that. They will have to accept it.
Tell a friend (or an adult if you're that desperate). They will help you figure something out.
Report them. Some people thing they are a cruel person if they report. It's scary for me to report people too, that's why I've never done it. It's hard for some people. (Only report if it is that bad).
Keep this one if none of the others work. This one is only for emergencies. Cyberbully them back,