I was a Personal trainer for over 15 years and more recently have been running Pilates studios here in Australia...lots of opportunities to scope out guys letting it all hang out while they train.
Unfortunately, I'm very professional and try not to look too much. I have, on occasion, asked certain men to wear different shorts so that the other members aren't put off. But I hate doing it, cuz it stops one of my few percs from happening!
However, when off-duty, I'm very happy to cop a look at a guys floppy cock and balls. I reckon it's on purpose, too. Come on, don't tell me they can't feel the air on their bits!!! So if I'm looking, it's cuz they want me to.