People use this phrase a lot.
If you decide to carefully point out an egregious flaw in someone's life, you might be rebutted with the Biblical maxim, "Judge not lest ye be judged."
But I think we're using that phrase the wrong way. That verse means you shouldn't be a hypocrite and throw someone under the bus who's doing the same things you do.
It doesn't mean you shouldn't judge the action itself. And it doesn't mean you should let your friends continue in their idiocy without pointing it out.