He wanted an image in his bedroom that would look like ejaculation, but not explicitly show that happening. He also had a fetish for leather, and a desire to shock. 
I think it was his mother he wanted to shock, but she wasn’t shocked, and she didn’t see the link between this image and ejaculation.
But you and I can. It’s quite obvious from the positioning of the beer bottle, the way that it has been shaken up to explosion and a little bubbly liquid allowed to seep out down the shaft.
Then you get the full leather gear, with the metal studs and gloves. It’s a brilliant image to hang up in your living space, and not to the queer fetish scene and a smirk at the climax. It’s available as a desaturated colour print, and goes well with browns, wood, tones, and dark walls. 
I seriously can’t wait for you to hang this on your wall!