I once came across a written conversation between two Muslims, one who is more liberal and the other who was not so much. I found this on a facebook group called Muslims Against the Desi/Arab Party Scene and someone posts “who are you to judge me?!” and the reply was “We are not Christians, Muslims judge! We were ordered to command good and forbid evil (amr bil m’arouf wa nahi ‘an al-munkar)!” I later reflected upon this and it blew my mind. Unfortunately, the condition of the contemporary man is that he associates advising with judging. This is a very potentially debilitating disease. The Arabs have a saying that goes “The camel sees everyone’s shadow except its own.” What this means (don’t worry, it made no sense to me either until my uncle explained it. It continues to make no sense.) that individuals do not see their own faults but see the faults of others. There are some people who are able to see nothing but their faults after a period of spiritual journeying but they have become far and few between. But even Imam al-Shafi’, as great as he was, when asked about his good character, said “I took what the critics said seriously.” I am asked to give speeches periodically at the local MSA meetings and I always want feedback so I can improve my speeches. One problem I find is that people always tell me a great job so I always find myself asking the Palestinian sisters (who never hold back on criticism, something I find very admirable in these times) for their feedback so my next speech can be better. I think all of the readers have similar experiences. The point is that we cannot do away with advise and people should not be offended when they receive it.
There is a group of people who I would also like to address: those who do not fully understand the idea of commanding good and forbidding evil. What they do is either judge and command harshly or insist that there is no other way than their way or a combination of both. For the the first group, I want to say that our beloved messenger Etiquettes of Disagreement CD three times already but that just shows its importance. There are shades of gray in Islam. I once was trying to do Mawlid in my university and there were some people, who did this out of the goodness of their hearts, were discouraging people from attending the Mawlid. Despite their good intentions, they were wrong to do this because there is no scholarly consensus on the impermissibity of the Mawlid. In fact, the majority of scholars encouraged it! Therefore, one should be open to differences of opinion.
As for general advice for commanding good and forbidding evil, the first thing one should do, aside from the aforementioned things, is ask about what happened. When I was in Syria I was borrowing a cell phone and the previous owner had a picture of Nancy Ajram on the background (Nancy Ajram is the Arab Brittney Spears for those of you who do not know). I kept trying to change it but all the commands were in Arabic so I have trouble figuring it out (reminiscent of U-571). Once my teacher saw this and (watch this step) he asked about it first! Many people who know less would yell at me and say something to the effect about me being a heedless deviant. Maybe there is something about the situation you do not know. Maybe that girl your Muslim (brother) friend is hugging is his sister. Always assume the best and do not command right and forbid evil until you are certain something is wrong. If I may go off on a tangent, this is why stating that Qasida Burda has shirk in it is absolutely impermissible. Before one assumes that what could possibly be interpreted as shirk in one way but interpreted to be good at the same time, one should assume good and then ask about it. Imam Busayri, writer of Qasida Burda, stated what he meant by his poems and it is not shirk. One cannot accuse someone of committing shirk without being absolutely sure of their shirk. (Summary of this paragraph: ask first)
The second piece of advice I would like to give is to know who you are talking to. If I am sitting with a very righteous brother and I see him eating with his left hand, I might give him a subtle hint to use his right hand because he is at that level where he would benefit from the advice. But if I was sitting with someone who is not a very practicing Muslim (maybe they neglect their obligatory prayers or something like that) and I saw them eating with their left hand, I would stay silent because this might drive him away from any potential he has of realizing spirituality by making him think that Islam is just some collection of details. So speak to people at their level.
I also suggest going through Imam Nawawi’s section, in Sheikh Nuh Kellers’s version of Reliance of the Traveler, on Commanding Right and Forbidding Wrong.
And Allah knows best.