I think they are just jealous because the Simpsons suck now, and Family Guy has taken over as the leader of animated comedy. Fucking sore losers! I hope Seth MacFarlane rips them a new one in his next episode.
Besides, I think South Park's "The Simpson's Did It" episode rings true here. There's no point accusing everybody in the world of copying off of The Simpsons, when the Simpsons have already done everything anyway.
Rosalina: But you didn't.
Robert: But I DON'T.
Rosalina: You sure that's right?
Robert: I was going to HAVE told you they'd come?
Rosalina: No.
Robert: The subjunctive?
Rosalina: That's not the subjunctive.
Robert: I don't think the syntax has been invented yet.
Rosalina: It would have had to have had been.
Robert: Had to have...had...been? That can't be right.