Well, I haven't really noticed the male fashion you describe with the boys at the middle school I teach at. A few try to hide in their big sweatshirts, but I make them take the hood off. It's really not an issue though.
Lise, I don't know why we generally think it's OK to see a bra line and not a panty line. I think there's 2 distinct issues here. One is when women wear thongs that stick out above the top of their pants, so you actually see the underwear and the other is just seeing panty lines of any type of underwear. I was describing the bulgy, panty line issue when discussing my original intention for wearing thongs. Generally this issue is worse when people wear pants and underwear that is too tight, or they are overweight. Any kind of underwear. I understand what you and others are talking about when you describe people (younger girls in particular) walking around with various parts of underwear, thongs, bras sticking out. We are having a major problem at school with girls wearing tight t shirts, with low cleavages, and a camisole underneath, that just doesn't cover up the cleavage. One mother we called said it was none of our business if her daughter dressed like that (this girl has C+ to D size boobs). Legally, we really can't tell anyone what to wear, but when i put the kids in literature groups with a girl dressed like that, the boys cannot focus. They get silly and weird; they are 12 and 13, and it's really hard for them to ignore a girl dressed like this. We were able to discuss this intelligently with other mothers who had no idea that their daughters were coming to school like this (they changed somewhere between home and school). Generally, I am against censoring things like this (I was the girl who came to school in jeans when we were not allowed to wear pants in the 60s), but it is distracting and it just sends the wrong message.
So, yes, I understand what some are upset about, but I wouldn't give up my thongs for anything. I hate underwear in general and have never worn it under ANY exercise clothes, long before I started cycling.