To be honest, the groin area is
not the most visually appealing area of a man. I might be checking out your arse, but I wouldn't be looking at your junk.
I only pay attention to that area on a man if it's gone beyond a certain point in physical contact. In the interest of not being too graphic, lets just say that's beyond hugging.
Unless someone's crotch happened to be in my eye line, or I can... ah, feel how pleased the chap is to see me, I don't notice it. And well, to be blunt, that sort of response seems to have a mind of it's own, even if I
did notice such an occurrence with one of my male friends, I'd chalk it up to the fact that it's maybe been a while for them, they just had contact with a reasonable looking female and sometimes your bodies just respond to relatively innocent stimuli, even if your brains really don't want that to happen.
Also on the boxers v briefs question, I can understand you wondering given the nature of your predicament - briefs certainly keep things more contained. Once you get to the clothes off stage though, boxers look better.