A good friend of mine is a comic, and through him I've met other comics. They'll often riff off of each other. Upon hearing something really funny, you'll often hear, "Hey, that's good! Can I steal that?" This is totally accepted and expected behavior among this group of comics. So stealing jokes, per se, is not the problem.
The troublesome part is that there's not a good way for other people outside this group of comics to join in and ask for permission. All they can do is listen to the material live, and then kinda take it if they think they can get away with it.
I'm not sure if this is a problem that needs to be solved, but it's easy to see where these misunderstandings might arise. Everyone copies and steals. Sometimes it's unclear or uncool to ask for permission.
This is all separate from the main article here, where I think it's clear the copier is a huge asshole. I also need to listen to that podcast.