It is the most common activity in all social settings. Sometimes it is explicit: we argue for or against something. At others it is implicit: we show interest or lack of interest. More often than we realize we are engaged in persuading others or are being persuaded by them about big and small things in life. It is a very powerful force also. That is why marketers yearn for word of mouth publicity and powerful media machines long for becoming the talk of the town.
Concerned with good as it is, Islam gives this tremendous social force a purpose. It must be used for promoting good, truth and justice and checking evil and injustice. That is the essence of amr-bil-maroof-wa-nahi-anil-munkar. And Qur'an declares it as the defining mission for this ummah:
At another place Qur'an declares promoting good as an attribute of believers and promoting evil as an attribute of hypocrites:
On the other hand,
The implications are clear. It is not that a believer will never commit a mistake or be involved in evil. Only that he will never insist on it, justify it, or promote it. He may fail to do some required good. But he will never be a force opposing it. In the Islamic society sin is a private weakness, not a public cause. It is for this reason that repentance for a public sin must also be made in public while we must repent privately for our private sins. A public sin may have encouraged others to do the same. A public repentance will counter that.