Play on the words 'yaoi' and 'retard'. It's a usually-derogatory term used to denote someone who has an obsessive or blind fixation on yaoi, whether or not the pairing in question is even probable. Yaoitards are usually n00bs, too.
There's an abundance of yaoitards in the Naruto fandom. Their presence makes me feel very, very violent.
Yaoitardation is a DISEASE, one that I am glad to have caught. <3