Never heard of Dahvie Vanity before. ED describes him as "having the writing skills of a 12-year-old and the singing skills of T-Pain," so I guess that explains him having fans like this.
He's the singer from an emo-dance band that was somewhat popular with underage girls and lonely fat chicks. They're mostly notable for being the band that started all the Jessi Slaughter drama a few years back.