Breastfeeding only leaves a milktache. If you can "pee in public" and not leave a stain, have at it. I doubt you can...;-)
Do you pee without unzipping your pants or something, since when does urinating leave a pee stain n your pants? Boxers or briefs, maybe. Well, unless you're not wearing any, but, who would ever want to give away the fact that there is only one article of clothing separating Wang's Auto Parts from the rest of the world.
Sure you can.
A man can urinate into a lidded urinal in public just as discretely as a woman can breastfeed in public. All it takes is a strategically placed piece of cloth.
Both are natural body functions involving parts of the human anatomy that are not usually displayed in public. The only difference is that breastfeeding is Politically Correct in 2005 while urination is not. Back in, say, 1955, both would have been equally shocking at a City Council meeting.