Let me follow the reasoning here:
Apparently, a significant bloc of Republican voters are so bigoted that they will not vote for a candidate with a gay family member. Therefore, the opposition party should never mention the existence of Republican candidates' gay family members, because it "unfairly" alienates that bloc.
There are many things wrong with that argument, but the obvious question would be: are you really that worried about the bigot vote? It seems to me that the moral wrong here is on the part of those who automatically exclude gays. Another point: what about the "anti-bigot" bloc of (presumably) mostly gay voters? Wouldn't Cheney's having a gay family member make them feel more comfortable about voting for the Republican ticket, by making it appear less likely that Cheney himself is a bigot?
Then, of course, we could point out the utter hypocrisy of Bush supporters crying foul over this matter. Surely they are aware that Bush and Rove started a whisper campaign against Ann Richards, who Bush defeated in the Texas gubernatorial race, on the basis that she was too "soft" on homosexuals and had appointed some to government positions.