@Mr_NutterButter i mean i'm not gay but the way i see it, a girl's nipples being visible under her shirt is relatively similar to a guy's dick being visible through his pants. both totally natural but also sexual things.

balls kind of go with the dick but are a bit more concealed. if a guy is specifically wearing like a banana hammock or something that really shows off the bulge though then it's pretty much the same thing, it's just you can't really get away with that in the same (or as many) contexts as a girl just not wearing a bra or showing a lot of cleavage.