What fallacy is this?

[Lonestar]

So, I've taken to posting on a message board that has strong Libertarian tendencies. There was a thread about best/worst Presidents and one of the Posters said:

I would never even try to judge Presidents from before my lifetime. Who writes the history books, you know?

Which responded with me saying:

You won't judge:
"John Marshall has made his decision, now let him enforce it!"?

To which he responded "No." So I commented that, following the logical extension of his premise that he can't judge people before he was alive then he must have a neutral view of Stalin and Hitler(yeah yeah, Godwin's law). His rebuttal was "This is a dumbass conversation. I don't judge Presidents before my time, deal with it."

Is this an actual fallacy? Or is he just being a retard?

[Kanastrous]

He's realized the dumb-assedness of his position, but refuses to admit it, and so walks away from the conversation.

I vote for 'retard.'

[Alyrium Denryle]

He is being a retard. But it looks like moving the goal posts, or at least that is what he would have tried to do had he not snapped at you

[Ted C]

Sounds like a form of Appeal to Motive, with a touch of Poisoning the Well.

He's basically saying that the accuracy of any historical account of a President will be biased because of the motives of the historians writing about that President.

Of course, there will probably be multiple historians with different biases, so it should be possible to reach an objective opinion by comparing multiple accounts from different sources, but he's ignoring that fact.