What is confusing is that you still seem interested in him after hearing that he called you a "stalker" to your mutual friends. If this guy even liked you as a friend, he wouldn't be calling you a stalker behind your back. That's pretty cold. It sounds like he was flirting with you and several other women at the same time because he's a big flirt and likes to get his ego stroke-- not because he was particularly interested in you or these other women.

Since you say that you want to understand this situation so you don't repeat it, the only thing I can suggest is not investing ANY emotional energy or interest in a guy who is flirting with other women in front of you. If he is flirting equally with you-- and someone else-- than he isn't really into you. He's just a flirt. If a guy is into you, he's not going to have eyes for anyone else at the same time. Similarly, if you find out he has called you names behind your back, that sound be the END of it. He doesn't respect you, so you should move on. Don't let anyone disrespect you like that. You want to go for the guy who is interested in you and treating you the same way to your face as he is treating you behind your back.