Rocker Pete Wentz has come to the defence of his pal Travis McCoy, insisting he did nothing wrong when he lashed out at a fan during a gig on Tuesday night.

The Gym Class Heroes frontman was midway through a set with his band in St. Louis, Missouri, when McCoy took offence to an audience member who reportedly called him a "f**king ignorant n**ger".

McCoy invited the concertgoer onstage, but when the unnamed man lunged at the singer, he went on the attack - and whacked the fan on the head with a microphone.

The outburst resulted in McCoy's arrest on a third degree assault charge immediately after the concert.

But Wentz is furious at the "pathetic" fan and claims his friend was not the one in the wrong.

In a post on his online blog on Thursday, Wentz says, "you know what? you call my friend a "n_gger", i dont even give a f_ck what happens to you. i dont want to see you in this scene. i dont want to see you at shows. you are who we write songs about. you are who we think about when we hate..."

"What a joke. you are f_cking pathetic and anyone that disagrees should put their white hood on too. I dont want your ticket money. I dont want your cd sales. I'd rather be poor and unknown."