[_h4xr]

Has anyone disputed them? This seems like a great example of an ad hominem attack--you haven't had to question their data, or their logic, just the fact that they've found an argument supporting their conclusions.

That's a good way to talk past people. If you're legitimately concerned with their views, this is a great opportunity to identify what flaws there are with this argument, instead of the ways you already disagreed with the conclusion.

I mean, think about this in terms of who is contributing to the argument. Vdare: "Here is some analysis of the data, revealing what may be surprising results!" You: "Like most people, I disagree with VDare's conclusions. I'm not going to address their arguments, and I'd like to warn others against doing so, too." Who is contributing, here?

[jdietrich]

Not an ad hominem. An ad hominem argument attacks the character of the speaker independent of the argument and is a specific subset of non sequitur.

Whether an organisation is racist or not is highly relevant to whether we should trust their findings on matters of race, in the same way that someone being a salesman is relevant to whether we should trust their opinion on products they are selling.

If the accusation was that they were homophobic or sexist or a bunch of drunkards, that would be ad hominem. As it is, pointing out that they are racist is a very relevant and useful contribution. Although we cannot assess the objective validity of their findings based on that fact, our assessment of the probabilities change greatly.

[Locke1689]

If the source started as disreputable then it is wise to weigh its conclusions lighter than more reputable sources. It's not an ad hominem attack, it's inductive reasoning.

[_h4xr]

It's still ad hominem, even if it's also inductive reasoning.

I'm still hoping for a follow-up addressing the claims, rather than the person making those claims.

[winestock]

If the disreputable source is the sole source for those claims, then, yes, one should hold the claims in less than high regard. But if that disreputable source points to a third party, then that party should be the one under condsideration.