Would it be better if I called it a "misconception" perhaps? If it matters, I meant it in the "idea that spreads between people" sense, not the animal-gif-with-block-text sense.

People are deserving of respect, arguments less so. I see no reason to grant any particular deference to a sentence.

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.