I think the issue here was not filth, but rather a cultural conflict in the US over attire. It's an indigenous thing.
There are two groups that resist conventional dress: rednecks and hipsters. I mean "rednecks" not in a disparaging way, but in the self-identifying way they use the term themselves. Think of it as anti-cosmopolitan culture -- country music, pickup trucks, and all that. My sardonic post was a spoof on them. It's not whether you wear a billed cap, but rather which one is appropriate for certain circumstances -- a black-tie/white-tie kind of thing.
If you frequent trendy restaurants in big cities, you run into another take on attire -- the hipsters. They're anti-establishment but very cosmopolitan. They might wear a corduroy cap with the name of an obscure Belgian craft brewery on it.
I sometimes wear suits and ties to piss both of them off. d8-)