Carl is harmless, he's not going to attack anyone. Carl likes to talk a lot of shit and mess with people, but he's doing it all as a joke. Tons of people have met Carl in person and he was never violent or aggressive, he just like to play guitar, shitcan gear and talk trash.
What a lot of people don't seem to understand is that Carl gets off on all these people talking about him. He trolls for people to get all worked up and someone always takes the bait. Then he messes with everyone and it gets out of hand and eventually he gets banned from whatever forum it happened on.
If nobody wanted Carl around then nobody would ever mention his name again, nobody would reference him, nobody would acknowledge him. But people need Carl as much as Carl need them. So the endless cycle continues.
I was trading insults with Carl online over a decade ago (before internet forums even existed) and I never took it seriously. I don't know Carl other than my online interactions with him, but I don't see why people get all upset about Carl. My policy is to let him do his thing, fire a few shots his way and trade a few insults every now and then, and basically we get along just fine. Try it, you might find Carl funny (in a sick way) instead of getting all worried about him.