Saying an argument is false because it's a meme isn't a rational way to argue against a thought. You argue against things with facts and evidence. It's more disrespectful of the opposition if that's the strongest remark the opposition can make.

I suppose the great-grandparent is more an 'appeal to emotion' fallacy rather than ad hominem.

The word "meme" isn't doing any argumentative work here. It's just a handle for the claim that's being contested, with some extra connotation that the claim is typical or customary rather than unique to this thread.