Joe Jonas turned 20 years old on Saturday. But the singer isn't in a celebratory mood today, as his lawyer has fired off a letter to Zack Taylor because that celebrity gossip blogger continues to insist that Jonas is slipping it to ex-girlfriend Demi Lovato. TMZ has published the document, which takes issue with an article on Taylor's website that states Joe and Demi are "friends with benefits." Due to the differences in the stars' ages, this is a dangerous accusation, one attorney Rob Cohen writes is "completely false, offensive and defamatory." Moreover, the letter (read it here) accuses Taylor of a "malicious attempt to attack and devalue [Joe's] good name and reputation." Joe and Demi broke up in May. They are currently touring together, which Jonas says is fine because they remain close friends. The singer's lawyer demands that Taylor remove the posting in question or face a lawsuit. In the meantime, Joe will continue to possibly court Ashley Greene, an actress of legal age who we're guessing he'd gladly be accused of giving it to.