The shock factor

A common element of punk is the idea of challenging previous norms, whether those be gender norms, political norms or behavior and appearance norms. One attempt at challenging these norms is to use shock, either to provoke a reaction and thought or to normalize something that was once considered taboo and because sexuality has many taboos associated with it, it is often used to get a reaction. By being blatantly explicit and wearing fetish wear, women's clothing and makeup, bands challenge the idea that only certain people wear these things. One example that has been making the rounds lately is a picture of Iggy Pop in a dress with the caption "I'm not ashamed to dress like a woman because I don't think it's shameful to be a woman" Found at: http://transcendboundaries.tumblr.com/post/16935258298/three-images-of-iggy-pop-in-a-dress-with-text

Iggy is hardly the first punk to dress like a woman onstage though. The New York Dolls regularly dressed in women's clothing, shoes and makeup and there is a whole genre called glam rock that revolves around dressing with items traditionally associated with women.

 

from  http://www.allstarpics.net/0113366/012143774/the-new-york-dolls-pic.html

Women's clothes aren't the only things used to shock, however. Rammstein, a German metal band known best for their song Du Hast has numerous songs with very explicit content and the performance of their song Buch Dich has gotten them banned from several venues. In this song the singer drags his band-mate around in bondage wear and pantomimes having anal sex with him. He pulls out a false penis that is connected to a pump full of custard and proceeds to douse the audience in "semen". (super explicit)

Still another example is the excessive use of words considered highly offensive. The band Orange put out a song on the Hellcat Record's album Give 'em the Boot 5 that is based entirely around the word cunt. Have a listen if you would:

http://grooveshark.com/s/I+m+A+C+T/2NpUD9?src=5

 The use of this shock technique is so common, in fact that it will likely be an integral part of punk forever. Challenging standards is a punk thing to do and since the vast majority of the public has sex, it's an easy way to shock just about everyone.