Forbidding wrong (Nahi Anil Munkar) is obligatory if it's conditions exist including the possibility of effect on the wrong doer, and safety from danger or harm.
Ruling 1868. The following five conditions must exist in order for enjoining good and forbidding evil to be obligatory.
1. One must have knowledge of what is good and what is evil, albeit in a general sense. Therefore, enjoining good and forbidding evil is not obligatory on someone who does not know what good and evil are and does not distinguish between them. Indeed, in order to enjoin good and forbid evil, it is sometimes obligatory to learn and know what is good and what is evil.
2. One must deem it probable that it will have an effect on the wrongdoer. Therefore, if he knows that his speech and words are ineffective, the well-known (mashhūr) opinion among jurists (fuqahāʾ) is that he is under no duty and it is not obligatory on him to enjoin good and forbid evil. However, the obligatory precaution (al-iḥtiyāṭ al-wājib) is that he must express in any way possible his disapproval and displeasure with the wrongdoer’s improper actions, even if he knows that it will not have any effect on him.
3. The wrongdoer must intend to continue doing the improper and wrong actions. Therefore, in the event that the wrongdoer does not want to repeat his wrong actions, it is not obligatory to enjoin him to good and to forbid him from evil.
4. The wrongdoer must not be legally excused (maʿdhūr) in his improper and wrong actions; i.e. he must not believe that the improper act he did was not unlawful and that it was permissible (mubāḥ); nor must he believe that the good act he abandoned was not obligatory.
However, if the evil deed is something that the Holy Legislator [Allah] is never pleased with – such as the killing of an innocent person – then it is obligatory to prevent it, even if the perpetrator is legally excused and even if he is not legally obliged to fulfil religious duties (mukallaf).
5. The person enjoining good and forbidding evil must not be in danger of significant harm being inflicted to his person, reputation, or wealth. Furthermore, it must not cause excessive difficulty (mashaqqah) or unendurable hardship, except in the case where the good or evil act in question is regarded by the Holy Legislator [Allah] as being so important that one must endure harm and hardship in its cause.
If the person who enjoins good and forbids evil is not in danger of any significant harm being inflicted on himself but other Muslims are – whether that be to their person, reputation, or wealth – then it does not become obligatory on him to enjoin good and forbid evil. In this situation, the level of harm must be compared with the act in question, and sometimes even when harm is caused, he will not be excused from enjoining good and forbidding evil.
Wassalam.
