Why do they do that?

Is it just me, or is IMing with teenagers becoming more of a problem that it should be? I am seriously thinking of banning it from our home! In one week (this week) I have read conversations between my daughters and others that I'm appalled at (yes, they let me read this!). The first one was between an 8th grade boy and my 7th grade daughter. He was trying to get her to admit she liked a boy that already had a girlfriend. She kept denying it and he kept getting nastier (sp?), using filthier and filthier language and attacking her character. I was truly disgusted by what he said. I told her to block him and she was no longer to talk to him, on the computer OR at school. I also said I was thinking about printing it out and showing his parents. She told him this before blocking him and he sent her an e-mail, apologizing all over the place, begging her to please ask me not to talk to his parents. I am still deciding on that one. Then last night, Ashley (who's a sophomore) asked me to come up to her room to see this exchange. Someone she didn't recognize IM'd her, saying she didn't deserve the guy she is seeing and that she was an "ugly, fat, whore". Then when Ashley asked who it was, they signed off. I suppose it's easier for kids to say what they think when they aren't facing someone in person, but this is getting ridiculous! I'm really ticked off as a parent and hurt that my kids had to be subjected to this! What's a parent to do????