David, Mugabe's thugs have used the rape of male detainees for sometime now. Male rape, the latest weapon for Mugabe's men

The aim in this case is to break the spirit and crush dissent rather than encourage radicalization.
In Congo Brazzaville, Bemba did the same with systematic man rape of chiefs and communities leaders. It is part of the crimes he is judge for in The Hage.
As for Mugabe, the aim was to break the individual will and put shame on them.
In DRC the pattern is little different and somehow closer to Yugoslavia. It is, at the beginning, ethnically based.
There has been quite some work done on SGBV in former Yugoslavia. I would be surprise if you find anything on man rape but some work may exist as Yugo was the starting point for the modern use and study of rape in war.
ICRC and MSF or MDM may have some publications. Especially if you look at SGBV and the Bosnian detainees.