Gentlemen, let me make one thing unequivocably clear. When I am peeing, I don't want to have a conversation with you. I don't want to say "hi", give you a head nod, discuss the weather or politics or my new shoes, or hear about your day. I most certainly don't want to make eye contact.
There are dividers between urinals for a reason. This isn't a bar and we're not in Europe. Please keep your eyes forward and your mouth closed.
When we're washing hands then minimal conversation is permitted, but even then let's keep it short and simple.
It's not that I'm insecure about my manhood or my sexuality, quite the contrary. I just feel that some things are personal, and taking a piss or dropping a deuce are two that rank very high up on the list. I don't come into your bedroom to chat when you are boning your wife, and I expect you to extend the same courtesy to me when I'm doing my business.
If you want to shoot the shit then hang out in the kitchen. My schedule is as follows: Kitchen for water or coffee - desk - bathroom. Repeat.