They are all sterile, not asexual, if they didn't had any genitals then the master would have probably thought about it twice before trying to replace all humans with supermutants
They do, they're just infertile. In Fallout 2 you can get raped by a Super Mutant if you can't beat him in an arm wrestling contest. We need Obsidian to remake 1 & 2, some crazy **** went down in those games.