I followed your link, then followed the link's link. The most objectionable costumes pictured were the "nude" family, where no one was nude, but the costumes were anatomically correct. Gross! Totally inappropriate for street wear at any age, IMO.
I also did not like the "bloody chicken" costume on the infant. I think babies should be dressed in cute costumes, not gross ones.
The rest of them were OK. The Hello Kitty perhaps showed a little too much skin, but no more than most high school girls are showing when they dress out of school. I'm not sure I'd be crazy about having my grade- or middle-school-aged kid wear the pimp outfit, or the terrorist bomber, but I've seen both those costumes on older young people and thought they were OK. (I've seen a high schooler dressed as a pimp, and a college student dressed as a terrorist, both at Halloween parties, not on the street.) I guess context is everything, but Halloween is a holiday that pushes the bounds of taste anyway.
As far as showing skin is concerned--I think kids (and moms) should remember that Halloween can be chilly, especially at night. I have never advocated letting my kids, or myself, dress in such a way that any of us were likely to get sick the next day. Of course, if you are going to be inside, that's not as much a concern. But most of those "shorty" costumes were accessorized with leggings, and I think something like that is the way to go. The can-can girl was adorable. I know that was a risky thing in the late 19th century, but today? It just seems like a fun costume.