I'm fine with sexy women in the PHB, but I feel like there's a line between "sexy" and "thinly disguised porn." It's hard to define exactly where that line is; but I think a lot of it derives from clothing that is obviously impractical for any purpose except looking sexy.
For example, I've got no problem with a portrayal of a female warrior in loincloth and leather halter (see Klaus's picture #2). Most people would prefer a little more protection, but if you don't want to be encumbered by armor and are in a fairly warm climate, it's not unreasonable.
On the other hand, put the same woman in pauldrons, greaves, gorget, vambraces, helm, and half a breastplate, with exposed midriff, cleavage, and a metal G-string (see Klaus's picture #1), and I have problems. Put her in a suggestive pose, and I have more problems. That outfit is providing all the drawbacks of armor--weight, loss of mobility, expense--with none of the benefits.
Similarly, high heels on adventuring women are ridiculous, at least while they're actually adventuring.