Brother in Deen
You have to be wise and call them to Islam, to raise their iman. Every person and situation is different. Someone who is evil and openly calls to evil, is a "threat" to those around them, whilst you also have people who know what they do is wrong and want to change, but need encouragement or help. Sometimes, people do not ask for help, they might even turn you away and say they do not need your help, when in fact, they want it, but their pride or emotions stop them from doing so. The worst thing to do is to abandon people or treat them in a bad way, when they cause no harm to you or your iman, it achieves nothing.
we agree in general, but this olso canot be don in all cases, both way's are done, and the limit is where Allah and Prophet alayhi salam made limit to it..
with what we measure danger, just from fear ?, our personal knowledge ?,from our nafs (desire)?, or first it comes from Quran and sunnah as sahaba understud and practis and thos that followed them?...answer is that the measure what is good and bad in dawah and what is danger in dawah we take it from the main sources as we mention..
scholars said when the dawah is in question, if we fear that we can fall in sin when we do dawah in one place, we leave the dawah and that place too, and we look for ourself to be saved...olso we have alot of fatwa that says for example, if father is filthy, and the daughter is feared that he will do harm to her, then its haram for her to stay with him and she can leave the house...
just the expresion of the filth wich they have its danger in it self, in islam harm is not just to attack in physical way, danger comes even from words and what person represents....
...why is so much sin and danger to lie upon a honest women?...one of the reason is that when one person lie about honor of one women, it open a way of bad thoughts for the people and thos that are weak in nafs-it opens them a way to haram, becasue now they know a place where to do haram (according to what the lie with they heard)...one of the reasons to hide sin is that-just by mention them, it can open a way to some who are weak to go into them, nafs is in danger always from temption of life...we are advice to put down the look so that we dont lead ourself to haram things..
to know more details on what we should do, each case has his own way's to do, so the person have to ask a person with knowledge the conditions and details, and the shaykh will inform the person how to deal with the case, we canot just generalise things and say " well he is not doing harm ", becasue as we mention just their expresion of the filth its danger itself and we can never be sure that that filth will not go into higher level...in west this things didnt apear for one day, first where different sins and this sins lead them to more differen sins, and now they are filled with sins..
sister Tabassum07 posted very very good explanation of this, it is in general ofcourse, but its a good explanation how to measure things, may Allah reward her with good, very good understanding of limits in dawah and hikmah-wisdom...as for more details, a person can ask a shaykh, as i said up