You are missing the bigger point. The ones who will vote for the rapist/felon/adulterer/scam artist are exactly who will vote against any gay candidate. They are the same demographic. And plenty of the silent middle that they keep talking about will refuse to vote for a gay person as well. I would bet at least 52-55% of the population, given a reasonably viable opponent, as in anyone other than Trump, would choose anyone else over a gay candidate. I am very certain that pitting Pete against Trump this year even, would just hand the presidency to the psycho. Do not underestimate the bigotry at play here. I disagree heartily that the majority of the middle will vote for a gay candidate, I believe it is just the opposite. We are generally a majority conservative country, but enough of those conservatives are moderates that given a nut-job like Trump they are willing to swing the other way for a single election. But they are still bigoted in many ways, especially against gays. So you will have some of the moderates vote for Pete more or less just to vote against Trump, but I believe the majority of them would vote against a gay candidate sooner than vote against Trump.
It is a weird dynamic in the moderates in our country no doubt. Many of them can see reality for what it is and therefore eschew Trump. But their deep-seated biases are still driving forces and plenty of them have deep-seated biases against gays. I would wager stronger than their biases even against minorities and women. So Harris has a chance, but I believe, given the current climate, Pete would have no chance.
I could very well be wrong, but that is my feeling especially given how many in my friend and acquaintance groups are more middle of the road conservatives. Plus looking at past voting records. Give them a straight, white, christian male that isn't firmly in the grip of dementia and he will beat Trump soundly. Give them a young minority woman and she likely beats Trump, but it is much closer. Give them a fringe group candidate, like a gay or mormon or anyone else they thing is just too much to deal with, and it turns the tide and they lose to Trump. It is just too much to ask of those in the middle who still carry those biases, which I think is a bigger group than we know.