will they ever learn?

So I have this friend I've known for over 3 years. I like being her friend, and have no interest in her in any other way.Recently she's been dating this guy. Bear in mind, I have never met him, but from what she has told me about him, I would have to conclude he's sleazy.Mistake #1--She works with himMistake #2--While he was dating another girl (pictures on his desk etc.), he took my friend home to her place and he went down on her. (No sex because that would be cheating--yeah right!)Mistake #3--When he broke up with his girlfriend, she started to date him.Mistake #4--One night while they were having (unprotected) sex at his house, he brought a sex toy to bed. Usually no big deal, but this was a USED sex toy!Mistake #5--She forgave him for trying to use the toy on her!Mistake #6--Recently, he went out of town on business. She had been wanting to see him as soon as he got back. On the phone he told her he was a little tired, and was going to meet up with an old friend and talk for a while--One of their co-workers saw him out at a restuarant with a strange (and really ugly) girl. Faced with getting caught, he fessed up to my friend the next day to being out on a date. (But he claims he didn't sleep with her) He also never mentioned that someone from the office saw them out together.Right Thing #1--She dumps him.Mistake #7--She took him back. "He's learned his lesson", "He's changed", "It's in the past", "He's taking me on a trip"I've just finished arguing with her about this crap. I told her that I trust her judgement implicitly when her emotions are not involved, but she obviously can't see how sleazy this guy is, and that when he cheated on his former girlfriend with her, she should have seen it coming. This whole trip thing shouldn't matter, and of course she claims it doesn't, but seriously, who is she trying to fool? I know there isn't crap for me to do, and that she really needs to learn her lesson. I'm just hoping that this asshole doesn't give her some STD in the process. She is a divorced single mom and this would prove to be a really stupid move.