I live in a Muslim country where most people have lost the Islaamic morals. It happens to me all the time to see a young man and a woman, who are not married, walking together with their arms around each other exactly like the Kuffars do. When no one is around I try to speak to them and advise them to show a some respect to those who share the street with them and tell the man that what he will not like someone to do to his sister he should not do to someone else's sister.
There are some brothers however that have advised me not to speak to them (the man and the woman) instantly and wait until I meet the man a different time then advise him while he is by himself. They argue that advising him in front of his girlfriend may be a bit disrespectful. I did not agree with them for two reasons:
First, I might not see the man another time.
Second, the advice is not only for the man but for the woman also. So my question to you is: Am I right doing what I am doing or should I listen to my friends' advice?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

First of all we thank you, brother, for your keenness to prevent the prohibitions of religion, and your enjoining good and forbidding evil. May Allaah reward you for this great act. Yes, you can continue to do what you have been doing, may Allaah increase your zeal. Continue to enjoin good and forbid evil but you have to abide by the Islamic requirements; meaning if your forbidding evil does not lead to a greater evil than the existing one. You have to forbid evil with wisdom and appropriate soft words, by admonishing and encouraging them about the benefit of performing acts of good deeds and reminding them about the danger and seriousness of committing sins. If you are quite sure that you will see the man again whom you saw with the woman, or that you know his house, then there is no harm to postpone advising him to another time when he will by alone, as this is more likely for him to accept the advice. You can give them influential tapes, leaflets and brochures which illustrate in general the danger of being in the presence of a marriageable woman without her Mahram (a non-marriageable relative). Do not forget to supplicate to Allaah to guide them, and do not be despaired from calling to Islam, supplicating, enjoining good and forbidding evil.

Allaah knows best.