What Rex obviously meant is that he didn't deserve a relationship, represented by the formerly universally accepted but now suddenly politically incorrect phrase, "getting a girlfriend". A phrase that is not remotely sexist on its own and that can, does and has travelled in both directions.

He was mentally unstable and wildly egotistical. He wouldn't have been able to carry on a relationship. That is why he didn't deserve one.

It wasn't society that made him murder four men and two women, it was his own mental issues. All of the claims that "the patriarchy" or misogyny are to blame for his murders are absurd.