When you become angry because you were wronged or insulted, and this shows on your face and you find that your loathing of that deed and the person who did it are more than your loathing of evil that you see or hear about, then know for certain that your faith is weak, and your honor and wealth are dearer to you than your religion.

You are permitted to remain silent if you know with certainty that if you enjoin good or forbid evil your words will neither be listened to nor accepted, or there will ensue obvious harm either to yourself or your property.

This is when enjoining and forbidden change from being an obligation into being a tremendous virtue which indicates that the one who does them loves God and prefers Him to all else. And if you come to know that an evil will increase if forbidden, or that the harm will involve other Muslims in addition to yourself, then the silence is better and, in some cases, obligatory.

[Al-Haddad, The Book of Assistance]