People in glass houses shouldn't throw stones.
People gather from this that they must either fortify themselves further against the world, turning their glass houses into concrete bunkers, or else cease from doing anything risky, and start being nice to everyone. It wouldn't occur to them that one doesn't need any kind of a protective structure at all.
Sages are creatures of the open air. They throw stones at glass houses.
Don't look for the splinter in the eye of another, when you have a plank in your own eye.
This means it is acceptable to have a plank in your own eye, as long as you don't directly give trouble to anyone else.