Marilyn Manson has been an absolute magnet for ridiculous rumors, however we can confirm that this one is true, unlike the rib removal rumor which bounced around in the 2000s. He has always been a man of fairly poor taste (e.g. cheating on ex-girlfriend, Dita) but this bold move was a little grotesque, which was a sentiment shared by Marilyn Manson's attorney.
The incident involved a security guard in Michigan who was unwillingly floored by Manson, before he rubbed his crotch on his head and made improper contact with him. Manson got off lightly with the charge of disorderly behavior, assault, and battery. Considering he could have been dubbed a sex offender we'd say he was lucky. He claimed it to be 'a victory for art'.