If you look at anime, you'll see that extreme-sized breasts with low-viscosity wave-motion physics attached to slender teenage females is kinda endemic to the "geek" entertainment (i.e. manga, anime, and video games) from Japan. I get disturbed by it, too, because real-life breasts, even extremely large ones, don't behave in the manner that is often portrayed (I can only guess that any woman would probably suffer a lot of pain if their breasts really did bounce and whip about to that degree). I'm not trying to excuse the portrayal, because it is completely unrealistic, but, I am saying that it's not just Team Ninja that does this.
It is true that, in general, human beings like sex (there may be a few that actually don't). We like having sex, we like thinking about sex, we like talking about sex, and we like being simulated by sexually provocative imagery and situations. But, there are healthy attitudes about sex, and there are unhealthy attitudes.
EDIT: Decided to remove the last statement in my comment. It was not as defensible and probably an attempt to read more into things that could be said, in general.