Thing is a person can be a Ladies Man and not think they are using a woman but then you have the women that fall in love with the Ladies Man and are hit with the cold reality that the Ladies Man wanted to have sex with them, not have a relationship with them. Now maybe they were a bit stupid (or a bit young) but if they called that man a Womanizer that's quite accurate to their experience.
People don't write out a contract clearly stating that this night of passion is only about sex and fun and not about a relationship. James T. Kirk certainly does not do this. He's extremely charismatic and the captain of a starship, I'm sure many women were hoping they would mean a lot more to him than a night of passion.
I'm not suggesting that ladies' men aren't part of harmful relationships. I agree: they often are. My point is that there is an important moral difference between those who set out to use someone and those who do not. And, to me, these two labels recognise this moral difference.
By the way, by noting this moral difference, I'm not absolving the ladies man of responsibility, e.g. for not recognising a lover's expectations (love) don't fit with his expectations (sex). I'm simply noting that there's a difference of intention, and that this is morally significant.
(It's also worth noting that both parties can sometimes
be equally deluded: he in his no-strings fantasy, she in her romance fantasy. It can be she & she and he & he, of course.)