> horny men just make do

Well yes, that's the whole point. In practice "make do" sex is all-too-likely to translate into abuse, driven by a mixture of sheer frustration (due to lack of the sought-after kind of sex partners) and a widespread culture based on physical domination within some toxic hierarchy of perceived masculinity. This is true both in prisons and elsewhere, e.g. in more general gender-segregated conditions as are common in some underdeveloped countries.