Shaykh Saalih Al-Fawzan – may Allah preserve him – said in clarifying the correct methodology in advising and forbidding evil:
Allah said regarding Musa and Harun (May peace be upon them both) when He sent them to Fir’aun, the tyrannical king: ‘So they (Musa and Harun) approached him (Fir’aun)’ and he did not say they stood at the markets and Masaajid and ridiculed him! Or they stood on the streets and gathering places and ridiculed Fir’aun because he overpowers people!
Rather He said: ‘So they (Musa and Harun) approached him (Fir’aun)’, and when you approach him: ‘So say, both of you, to him a gentle speech so that he may be reminded or fear (Allah)’. Because he was a person who would commit evil, so do not anger him with harshness and arrogance, even though he was a disbelieving infidel! However, gentle speech affects mankind so (when you speak to him in this manner), at the very least, it would reduce his evil and reduce his oppression and would make him open to the acceptance of the truth.
Taken from his treatise ‘Mafhoomul-Bay’ah’.
Translated by Hussain Suleman Abdul Sattar.