What's up with some married men chasing single girls?

[D]

My story is pretty pathetic... I feel moronic, really, because by now I should know better. I got involved with this handsome, charming man a while ago. He's from my college and he just started chasing me around. After I got divorced, I'd never been with anyone. I was just going along with my life, going to school, working, taking care of myself. I have no family, so I have a few good friends. So back to this guy... he charmed himself into my life, and we started going out for dinners, romantic walks, etc. One day, sure enough, we ended up sleeping together. Then another occasion again. Then after this second time, he just completely changed. A friend and I did some investigations on him, we found out through another classmate that he's still married and living with his wife and 2 kids. I was so furious. I asked him one day, he said they're separated but living under the same roof because he lost his job, because of the poor kids, etc. A bunch of lame excuses. Now he sees me in college and pretend nothing happened. Mind you, he was texting, emailing me all day long, all kinds of romantic things you can imagine, taking me out on romantic dinners, singing for me, etc. I feel really stupid because I could not figure that all this was a big show he put on just to get me in bed with him. After he got what he wanted, i guess he dumped me. We also found out his wife's facebook (she's not on his facebook contact list), and she just posted a picture yesterday of his birthday which was yesterday. They went out as a family, and she posted on her facebook: happy birthday to my loving husband, love you baby. And the last time I talked to him he said that "she's not my wife... we are separated. She's the mother of my kids, that's it." This is just so ridiculous. Why do some married men do that? Why put on this act? Why say "mother of my kids" knowing that he's still fully married with her? I wonder if she knows what he's saying about her... I felt really sick of my stomach when I saw that. I must have been really naive and stupid to believe this man. I want nothing to do with him now, I'm done. But, WHY?
I want to tell her and I even saved some of his texts too... I will show her. If I were in her shoes, I would also like to know.
Any suggestions on how I should approach her? Should I go to her house? we also found out where they live... I'm afraid she might want to beat me up!

[TheycallmeMom]

His wife deserves to know. I would tell her..and tell her he said they are seperated..and you just feel she deserved to know. Dust your hands and be done. Men like that do it because they get away with it. Bottom line. And because no offense girls like you Dont say anything. So he just did it
.and will probably do it to her again. He doesnt deserve a wife.

[Larissa]

what a dog! if only u has filmed it to show her! alas show her the emails!