I can see where you're coming from, bro. But as you said; the majority of Miley's fandom is comprised of girls my age. And what do girls my age do? Follow trends. Most teenage girls, at least, that I have seen follow the new 'let's look sexy' trend, and I have to say I was even convinced to follow it myself, but I decided it wasn't right from me.
If you can see what I'm saying, most girls my age are very influenced by bigger, popular people. I'm not saying Miley is going to make thousands of girls lose their virginity, since some girls actually have their own opinions, but she, Rihanna, Lady Gaga, and others are definately pushing most of the swaggy-girls towards it.