I think a lot of them are just kidding around and jumping on the bandwagon. They realize that making fun of Crosby is all the rage among non-Penguins fans nowadays, and they jump right on it.
Nothing new for anyone here though. I think it's fair to say that 95% of all Crosby bashing is born out of pure jealousy so there's no reason to really bring this up in my opinion.
Let 'em have fun for now. In a few years they'll be praying that somehow Crosby ends up on their team, which will probably never happen if the Penguins get a new arena.