In فَلْيَقُلْ خَيْرًا, خَيْرًا means something good. أَوْ لِيَصْمُتْ means “or let them remain silent.” This does not forbid necessary testimony, helpful questions, truthful advice, or speaking against injustice.
Example 1: Not forwarding an unverified accusation protects others from harm.
Example 2: Speaking up appropriately when someone is wronged may itself be the good speech required.
The measure is not how often one speaks, but whether speech is true, helpful, and responsible.