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.

That central argument you're talking about doesn't look like it was aimed at Grubber's case. I don't see any disagreement with Gruber's post. I believe it's an attack against Gruber himself, that says the hypocritical bastard got it coming, and even shares some responsibility for advocating the brand that single handedly popularised that kind of lock down.