Wow this all really sucks. I use photo references when creating fanart, but it's a reference only, not a copy. I can't imagine using anyone's actual artwork this way.

I mean, certainly it's rife in the writing sector of fandom, but artwork? Wow, I had no idea.

Is it because manips aren't really seen as artwork by the plagiarized? Perhaps they're unaware they're committing plagiary if the manip isn't signed or something? It's easy to come across something you don't know the origin of, I guess.

Though it does sound like this particular guy was unrepentant.