I'm not clear on how the cartoon as described relates to holocaust denial. It's nonsense, of course. No one is preventing Omar and Tlaib from speaking. That said, there appears to be no reference to the Holocaust in the cartoon.I think it was rather generous of Israel to grant Tlaib a visa to visit her grandmother. I suppose that when she requested it, she didn't really want it to be granted. Perhaps she was looking to score some "victim" points.