It isn't surprising, but it doesn't make it any less wrong. You're really going to insult someone's mother like that, and just because they didn't agree with you. You have no remorse for it because it's the Internet, so you got away with the insult and went on like nothing happened.
But I'm telling you now, if I were him and this were real life, I'd be happy to beat you down. You think you're funny and cute for posting crap like that and forgetting about it a minute later, but you're wrong. You may have gotten away with that shit, but I hope one day you learn to treat people better than that.
Otherwise someone's gonna beat your ass. But that's why you keep it online, right? Because you know what would happen if you did say something like that in real life. And that's fucking pathetic to me. You're just like so many other people on this site, a fucking coward.