Have you read fifty shades? I find that people like to bag on stuff they've never actually experienced first hand.
The reason that 50 Shades of Grey is subjected to highbrow literary scrutiny, is that it pretends to be highbrow literature. Male pornography usually makes no pretense, being more along the lines of logjammin' "ich bin here to fix your kable"
That's the patriarchy angle, if you actually want it.
Male porn is just porn, but "50 shades of gray" is presented as it is a regular book...
It's also 20 levels below in writing quality, like a messed up straight 20,000 lines amateur PHP monstrosity compared to something written by Rich Hickey.