Gittin Tzadik Amud Alef
Take a look at the case of Pappas ben Yehuda who kept his wife locked up all the time, and what happened because of that.
The Gemara advises a reasonable middle course for most people, not being comfortable with obscene behavior, but not going to extremes either.
Extremes of either side are dangerous.
If you crack down on teenagers, boys or girls, too much, they may start doing much worse things behind your back. Allowing them a reasonable amount of freedom for permitted things is healthier.
We don’t have a Tznius crisis. We have a common sense crisis.