it depends what you consid to be friends, and the ocasion in wich you 'show' it... like, if you're in the locker room or something, and everyones just showered, ok, you can toy and joke arounf flounting your cock to all to see, but if it's like, a dinner at your house and you, sudenly, decided to show it.. well, that's weird!
and then there's the gay factor... if you're gay, or at least are in a gay group, maybe showing off your assets may be a thing one could do, in like, trying to see if you 'got it'... [argh.. horrible reason...], cause if not, and even if you,re the meaty friend, well, showing your cock, isn't the most natural thing to do..
well, but if you're in a bath house.. that's allowed!