"Sure Donald Trump said vile things but Bill Clinton did them."
The first problem with this is that it assumes Don John didn't do anything. That's dubious. But there's a deeper problem with this that gets to a theme in the GOP.
If you think that an affair and sexual assault is equivalent, you don't appreciate the importance of consent. Sometimes a woman wants sexual attention. Sometimes she doesn't. If she doesn't want your sexual attention, just about anything you say or do is at the very least offensive and might even be abusive. If she does want it, usually anything you say or do is fine. Assault is less about where you touch than whether or not the woman welcomes your touch. Woman's consent makes all the difference.
But this gets to the theme in the GOP: woman's will isn't that important. Most conservatives roughly fifty years ago thought that women shouldn't have access to contraceptives. Most conservatives today think they shouldn't have access to abortion. Some even to this day think that it's not possible for a man to rape his wife. And now we see that quite a few believe that there is no difference between an affair and assault. This fits a pattern.
[And lest you point out that an affair is rarely consented to by the wife, I'll readily agree. Still, if we're comparing a married man engaged in assault and a married man engaged in an affair, the wife's lack of consent is a constant.]