So what’s all this beef about with Marilyn Manson and Justin Bieber?

If you were paying attention, the 48 year old slammed the 23 year old during a recent interview… saying he doesn’t like to fight with girls, so he doesn’t want to fight with Bieber.

But back in September it was a different story.

Manson opened up to Billboard Magazine about what initially started the feud – and it stems from when Bieber selling Purpose Tour shirts with an unauthorized image of Manson for a 195 bucks a pop.

During that Billboard interview Manson said that he was at a celebrity bar and saw a little girl in a pink hoodie and blonde hair… then realized it was Beiber. So he sat down and confronted him about the swag.

Justin played it like he made Manson relevant again… and the shock rocker said Justin was a real piece of you-know-what.

But in the end, Bieber’s company knew they were wrong and told Marilyn to take as much money as he wanted.

But when asked about the merchandise recently… Marilyn said he didn’t know because he doesn’t have the mind of a squirrel.

Your move Justin.