It is not zeal. It is that I understand your argument perfectly, and I happen to believe it makes insufficient sense, at least regarding the second half, regarding also overlooking Trump's behavior.
IMO, I can imagine what leaving Bill's personal life out of the discussion could actually mean, whether I personally like, love, or hate the man. He followed a fairly common pattern of less than perfectly honest politicians trying to keep his private life private. There was a woman who changed her story long after the statute of limitations passed on the alleged sexual assault incident -- that stays in the past, and I did not make assumptions about anyone involved, positive or negative. Reasonable people can disagree there, but we can at least agree or disagree about where to draw the line based on some coherent discussion.
But when it comes to Trump, what the heck is personal life and what is public, where to draw the line, is completely ambiguous. Is insulting a beauty queen and making a racist joke about her personal or professional? I could list a dozen examples in a similar vein. Badmouthing people, getting away with whatever he can get away with because he is "smart" and a "winner" is both the man and the message. Trump literally cannot answer a softball question about how to replace Obamacare without falling into an incoherent blather. All the man has is his big mouth and no plans and no policies. So which absurd badmouthing and bullying is it okay to talk about? Should I cut him slack on the bragging about sexual assaults? Why?
Trump steps over lines of behavior as a purposeful gambit to play the media. If he wants to run a campaign where the usual moral goalposts are installed on a moving cart, then it is not possible for an honest man to give Trump's personal life the benefit of the doubt in the usual manner. Even if I wanted to try, I do not know how. He makes things personal as a strategic choice, and such is a natural consequence --- unfortunately for him, sometimes life is fair that way.
When you were suggesting we could cut Trump slack in his personal life, do you actually have an idea where to draw the line? Do you have a clear idea why that would be the right place to draw the line? Based on what? Tradition? A manufactured sense of fairness that so happens to hide away and normalize bizarre behavior?