What is the ruling on criticizing the rulers?

Question:
I advised a man against criticizing the rulers, so he boycotted me because of that. When I met him in a place, I greeted him, but he did not return the greeting. After that, I boycotted him. Am I sinful for doing so?

Answer:
Answer: This is from the Khawarij. The one who incites against the rulers is from the Khawarij—may Allah protect us from that—so this is not permissible for him. The rulers have a right. Do you live without rulers? O, the glory of Allah! This is possible: he sleeps in his house and walks in the markets without the presence of rulers. By necessity, he is in need of the rulers. No one is free from needing them. They are called upon for good, they are supported, and they are obeyed in other than disobedience to Allah. They are not to be insulted with words or belittled in the eyes of people. This is the action of the Khawarij whom the Companions fought. They fought them because they spread corruption in the land. So you are correct in advising him, and you are correct in boycotting him if he does not accept the advice. And this is not enough; rather, it is obligatory for you to warn against him and make his matter clear, along with his followers, so that they are restrained.