The quote doesn't make it an allegation, that's right. The other parts do ("[...] that he has advocated for truly awful practices"). That "fact" is not part of the question and as such can only be refuted by invalidating the whole comment, not by answering the question (I hope that makes sense). A real (fair) question would have been something like "Here's a quote - what do you think about it?". Besides, again, it's not the right occasion.