Wikipedia agrees it's an ad hominen, but NOT fallacious (if true): "However, in some cases, ad hominem attacks can be non-fallacious; i.e., if the attack on the

Wikipedia agrees it's an ad hominen, but NOT fallacious (if true): "However, in some cases, ad hominem attacks can be non-fallacious; i.e., if the attack on the character of the person is directly tackling the argument itself. For example, if the truth of the argument relies on the truthfulness of the person making the argument—rather than known facts—then pointing out that the person has previously lied is not a fallacious argument." Lied and contradicted oneself are a close-enough match - but outright contradictions are rare; complex opinions and judgments common.