Many that call themselves Christians, don't understand this Scripture. Many Non-Christians employ this Scripture to silence, or control speech. What should be the Standard, is keeping silent, even in the modern-church. "See something; Say something" - and get a smack down!
When Immanuel-Christ-Jesus[ICJ] said "You sit in the seat of Moses" this is key in identifying the fakes. "Judge Not"[Matt.7:1, Lk.6:37] is actually condemnation. ICJ did not come to condemn, but to Save. We should not pronounce judgment, i.e. A person is worthless, beyond Salvation, dam-you, ...
A witness to some one's actions is totally different. If one doesn't understand Judge Not of Matt.7:1, flip over to Lk.6:37 for a better understanding.
ICJ came with Grace and Truth, to Save the world from Death[Gen2:16,7]: We nor the Church can Not Save anyone - so let us Not play Savior, and condemn what the LORD is attempting to Save.