The usual feminist meaning of "rape culture" these days doesn't include prison rape (at least not when it's happening to men). Indeed, I've seen people labelled as anti-feminists and misogynists for suggesting it does. It usually though not always encompasses prison rape jokes because those are considered to harm women, but not the rape itself.

From a modern feminist perspective, billboards of scantily-clad women have more to do with rape than men being non-consensually forced into sex.