I find it very... surprising that on LW someone can quote Philippe De Villiers, who is a representative of our extreme right, a fundamentalist Catholic and openly racist and homophobe.

In this context, his value system isn't the issue. There's nothing that Vladimir is using that's a questionable claim. He linked to an article which quotes De Villiers and doesn't say something like "oh, and mainstream scholars think this is bullcrap"- because the events unquestionably occurred. In fact the article quotes mainstream historians as agreeing with De Villiers on the factual history. The only reason De Villiers is bringing it up is for his own political goals. But that doesn't impact the factual accuracy of the points.

In general, it is a hallmark of rationality to take facts where they come from even when they come from very distasteful sources. Thus, we've had in our rationality quotes threads quotes from people as diverse as Jack Chick, Ted Kaczynski, C. S. Lewis, and G.K. Chesterton.

Sure, in the case of De Villiers if he made a specific factual claim and was the primary source for that claim I'd be less inclined to trust it than if say Richard Dawkins made the same statement but that's completely distinct from someone happening to be willing to cite an article that De Villiers appears in.

Politics is the mind-killer.