> GP is correct that the argument contains an informal fallacy The GP didn't say that. As for which informal fallacy the GGP's argument contained, I would say

> GP is correct that the argument contains an informal fallacy The GP didn't say that. As for which informal fallacy the GGP's argument contained, I would say it was more like a false dilemma. And the GGP did say "almost tautological", which implicitly recognizes that there might be other possibilities. > people often express this criticism by saying "your argument is tautological," I have never seen this (nonsensical) way of expressing the criticism that an argument is false by saying that it is tautological (and therefore true).