Yeah, some guys ARE assholes. If one's predominant mode of interaction with others is cruel and abusive, one is an asshole, plain and simple.
And if one does not discriminate with whom one engages in sexual behavior regardless of how one is treated by one's partners, but instead persists in a desperate effort, not only to satisfy one's actual libido, but also to receive validation from the sexual act alone, one is a slut. This does NOT actually require that one be promiscuous, but the correlation is high.
Women can be assholes. Men can be sluts. We usually note the reverse; I'm not convinced it is more prevalent.
I was guilty, at one point in my life, of being a slut who was attached to an asshole. I'm not proud of that, but I HAVE LEARNED from my mistakes. I hope. Now I tread carefully. But I'm an unreformed FLIRT, so beware.