I can only vaguely guess that the previous suggestions are probably right, though it is pretty mystifying.
However, I think you've missed an important distinction -- he said any guy would understand, not any man. I'm not sure exactly what guys are, but I've gotten the idea from the media that they're a certain type of male creature that share strong (perhaps extreme) enthusiasm for sports, and certain attitudes toward women (excuse me, "chicks") and various other characteristics. As far as I can tell, I have never been a guy, so it doesn't trouble me that I fail to understand this particular piece of guy-groupthink.
"Guys"
However, I think you've missed an important distinction -- he said any guy would understand, not any man. I'm not sure exactly what guys are, but I've gotten the idea from the media that they're a certain type of male creature that share strong (perhaps extreme) enthusiasm for sports, and certain attitudes toward women (excuse me, "chicks") and various other characteristics. As far as I can tell, I have never been a guy, so it doesn't trouble me that I fail to understand this particular piece of guy-groupthink.