What a man cannot say in daylight rules him in the dark. When he hides his highest commitment to keep the crowd comfortable, he does not merely stay quiet. He trades the thing that could redeem him for a moment of belonging, and the trade compounds. Every silence teaches him that his convictions are negotiable, until he no longer knows what he stands for.
The warning here is symmetrical, and precise. Betray the good you know and the good withdraws from you, not as punishment but as consequence. A man who will not defend what he values in front of others has already abandoned it in private. Speak for what matters to you, out loud, or watch it quietly stop being yours.