If, by "cheating," you're referring almost exclusively to romantic and sexual infidelity...

I've never done it (although my quantity of relationships has been minimal, in the first place, so I can't claim to be an expert). But if I ever did have a boyfriend or husband who admitted to cheating on me...the first thing I'd wonder is why he didn't come to me earlier and express dissatisfaction with how things were going in our relationship. I'd probably also wonder whether he was trying to communicate such a sentiment to me, and if I just wasn't HEARING him, for whatever reason.

If I ever had a platonic male friend who confided in my that he has cheated on his significant other...yes, I'd internally pass judgment on him. But, if he's my friend (or even a casual "friendquaintance"), I'd offer to talk through it with him.

As far as your question about whether admitting to the sin makes a male cheater "less of a man" -- I don't view it as my place to publicly/orally pass judgment on another dude's so-called "manhood." I'm a masculist...which means that, while I have my viewpoint on what qualities and traits usually make one's masculinity nutric (rather than toxic), it also isn't appropriate for me to dictate the definition of "manhood" for all of the other members of my sex/gender.