Riyad-us-Saliheen 194
Abu Sa'id Al-Khudri (May Allah bepleased with him) reported: The Prophet (PBUH) said, "The best type of Jihad (striving in the way of Allah) is speaking a true word in the presence of a tyrant ruler."
[Abu Dawud and At-Tirmidhi]
Jihad has many degrees. Preaching of virtue is also Jihad. The most meritorious of all is the effort of communicating the Message of Allah to an unjust ruler. Similarly, if a society is so much given to a vice that no one can dare to utter a word against it, then to protest against it can also be reckoned as the best Jihad.