Speaking of body hair, I'm normally pretty persnickety about this sort of thing--don't get me started on visible clip-on bow ties at black tie parties--but I'm not sure I can fall in line with this post (via Ann Althouse). I can see arguing that grown men shouldn't wear shorts because it violates adult etiquette. I can see pointing out that shorts flatter well-shaped legs and don't flatter dumpy ones. Hell, attractiveness isn't even always the issue. I've been fighting with friends who tell me I should show more chest hair when we go out for years. My relatively smooth buddies can have three buttons open, and you don't even notice. I have three buttons open, and I look as if I should have a sign around my neck that says, "Ask about my low all-night rates!"
But looking decent and looking comely are two different, if related, considerations that it's not good to slush together. (Is it proposed that we go the whole way and ask people who lost the genetic lottery on bone structure and complexion to wear paper bags over their heads?) Noisome breath and body odor or noisy chewing--that sort of thing is inescapable to people around you, so it's flat-out inconsiderate to inflict it on them. I have a hard time equating that with covering up your legs lest someone deem them too hairy.

Something else that bears mention: Plane travel is no longer a special event; now it's like getting on the bus. I'm happy to lament the general decrease in formality, but I think the cheapening of air travel has overall been a very good thing, and that in that case it's worth conceding relaxed rules and not getting exercised over casual attire. (Of course, you still shouldn't show up looking indecent.)
No one is forcing you to look...
But this involves taste, and people disagree. I'd never advocate laws, but when I'm flying I try to look as professional as I can.