Thats the exact thing that happened to me. Fucking moderators there. Me and two other Newgrounds (LightAndDark and EARIO) went on iScribble and we were joking around, we drew the NG tank, some cocks, all that.
Some guy says stop it, we didnt' really listen to him. He then booted EARIO out, then he said he was a mod. We didn't stop, EARIO came back and we drew cocks. The he banned EARIO, I got pissed that I just drew cocks even more.
He banned me, then LightAndDark. Then, later LightandDark asked "can't we make a private room?"...he says yes...he was an asshole for not telling us to make a private chatroom earlier on. Whatever, iSketch is better.