There ought to be "women only," and, for that matter, "men only" yoga classes available for those who don't want members of the opposite sex staring at them. But look, if you're in mixed company wearing very tight clothing, and you have a beautiful body, members of the opposite sex (and probably some members of the same sex) are going to stare. They aren't wrong for doing that. A little immature or sad, maybe, but not wrong.