Why did my ex write something mean about me?

[Christina]

My ex dumped me 6 months ago. The reason he dumped me was because I refused to have sex with him. He found it hard to cope with that I was a virgin and wanted to wait. However, afterwards he started insulting me on twitter and his blog. I decided to delete him as a friend on fb and cut all contact with him. About two weeks ago though I saw on his twitter that he had retweeted 'How to piss off a girl? tell her to call your ex girlfriend and get advice on how to give a blowjob'. Why would he tweet something so insulting about me? He's acting like he's not over me. Btw I'm seeing someone and I definitely don't want to get back together with him.