Hi Dorothea, I enjoy your comments so much. You are right about grumbling. Jehovah wants a balance. While we should not grumble against one another, we should nevertheless correct some who are on a wrong path if it is the right opportunity. Sometimes that correction comes with just not giving in to wrong behavior.
Galatians 6:1: “Brothers, even if a man takes a false step before he is aware of it, you who have spiritual qualifications try to readjust such a man in a spirit of mildness. But keep an eye on yourself, for fear you too may be tempted”
This harmonizes with Jehovah‘s principle set out Ezekiel 3:9 about warning the wicked. So, there are times when we should warn people, even our brothers and sisters, away from a sinful course, but I think that is different than grumbling. Just setting a good example is often enough.