Calling people to Islam as well as enjoining them to what is right and forbidding what is wrong is a duty upon the Muslims. The evidence for this comes in the following texts:

“Call to the way of your Lord with wisdom and beautiful preaching and argue with them in the best of manners.” [Sûrah al-Nahl: 125]“You are the best of nations brought forth for humanity. You call to what is right and forbid what is wrong.” [Sûrah Âl `Imrân: 110]
“Let there arise from you a band of people who invite to what is good, enjoin what is right, and forbid what is wrong. These are the successful ones.” [Sûrah Âl `Imrân: 104]

Allah’s Messenger (peace be upon him) said: “Whoever among you sees something wrong should change it with his hands. If he is unable, then with his tongue. If he is unable, then in his heart, and that is the weakest of faith.”

islamtoday.com

Wonderful thread. Very informative and alot of wisdom. Masha'Allah.