Can a man be a SLUT or is it only women who qualify? Why?

I wouldnt call a man or a woman a SLUT at any time. I have more manners than that!

Women only according to the dictionary. Men can be 'mimbos' though.

I had a buddy who qualified as a male slut. He claimed over 1000 bedded women. In fact, one of his wedding nights had his wife working her regular night shift while he was celebrating his wedding night in another woman's bed!  Then another time he had some sort of agreement between a husband and wife. He would 'make love' to the wife to show how good he was while the husband drove his car around the outside of the house. Makes no sense! He also 'stole' my girlfriend. Of course, this is when we were 13-14 years old. I didn't mind since I wasn't really too interested in her anyway. When they were a little older, they got married and had kids. I don't recall how many times he was married.

"No" ... Slut is generally a term for a woman or girl and is rarely used to refer to men, generally requiring clarification by use of the terms male slut or man whore.

Slut was originally a term for a lazy woman with poor standards of cleanliness - a man with those attributes was called a slob and still is. Like "gay", the definition has become sexually charged over time.
It's a common lament that "slut has no male equivalent", as a man who has multiple casual partners is held up as something of a paragon, a man to be admired. Indeed, if a man doesn't have a preference for generalized carnage in both his professional and social life, there must be something "wrong" with him. He's a sissy, a wimp. Lousy in bed, so nobody wants him.
Attitudes are changing, but it will be a long time before they even approach parity.

A man can be a slut as well as a b1tch, but I prefer to call them spoogebag$.