Why are guys (even nudists) so afraid of accidentally catching a glimpse of other guys' dicks?

The other day just as I arrived at the nude beach parking lot, there was an SUV parked a little ways away from the nearest car, so it was kind of out there like it was the only car in the vincinity. It was on a narrow strip of earth and small bush that runs parallel to the asphalt road, and facing a rock wall so high you can't see the top of it. Two men were just coming from the beach and crossing the road to get to it. As they were ready to get in on either side, one of them said something to the other and walked up to the hood of their truck. He stood still there facing the rock, in a wide open stance with his hands in his crotch. He was obviously taking a piss. Meanwhile, the other man, who was about to get in the SUV, made it a point to close the door and walk back to the tailgate, instead of climbing into the cabin or waiting for his friend beside the door like he was before. Then he stood awkwardly facing straight ahead at the sea. This all happened quickly as I was still on the road getting closer and closer to the parking lot. He must have heard my car rolling towards them and looked instinctively, like you do when you're just waiting, but immediately faced forward again, before I was even past them. His body language screamed "Nooooo I'll see my buddy's dick! Abort! Abort! Abort!" when his eyes were briefly pointed about 120 degrees away from his friend's direction, instead of 180. He was clearly embarrassed of this terrible mistake. Now think about it. The guy who was peeing had his back to this man. Even if the guy by the rear tire stared full on at the other one, he wouldn't be able to see a penis or a ballsack. Lest we forget: they were just coming back to the parking lot at a nude beach, for fuck's sake. Like what was he so afraid of anyway? What are guys afraid of when they see that every urinal with no neighbouring dudes is taken and they either sheepishly go in the toilet stall or leave the facility without relieving themselves? Is it about "going gay" like that's a real thing? Or is it about being perceived as gay by another guy who knows you're not because he too goes through that experience and it doesn't make him "go gay"? I don't understand it. I couldn't care less if somebody sees my genitals. I'm a nudist. And when I gotta go I gotta go. If you gotta go too, I'd much rather we do it simultaneously than take turns and waste more time than we need to just because of some silly insecurity regarding masculinity and the threat of homosexuality. Like... dude, that's not how any of this works. You won't go gay because you saw a penis or because yours was seen. Especially after seeing his whole naked body (not just his cock) and showing everything of your own too. Some guys are so fragile it's childish.