Oh wow.. another "heard this before"!
Happened frequently, by one guy in particular, at parties, and just about anywhere he thought it was ok by a guy on my football team. Was he just proud of his junk, or a future sex offender? DOnt know, dont care. His flaccid was offensively large. Maybe he got a lot of trim for the gesture?
A history book I had for class noted LBJ (liberal) used to do this sort of thing in his college days as well.