Asking ANY questions about ancestors should be off base, whether they are Jewish, Chinese, black, or little green men from outer space. Allen was right on to tell the reporter to focus on something that matters--like the issues.
Maybe so but, by characterizing the question as "an aspersion", he jumped the political shark.
Take a question about a hypothetical black ancestor:
An answer along the lines of "(Yes - No), my grandfather (was - was not) black. Did you have any policy questions?" is what America expects from a 21st Century American politicians.
Replying that the reporter should refrain from "making aspersions" is the same as answering "How dare you imply I have black blood coursing through my veins?" That is the answer you would expect from a David Duke.