Virtues and rewards of making salaam

You should tell them that the sunnah is that when you meet someone, you should greet them with salaam. There are many virtues and rewards mentioned in the mubaarak Ahaadith for those who greet people with salaam, and especially for those who greet people first.

Tell them why should they deprive themselves from practising on this sunnah and from acquiring the great virtues and rewards promised for those who make salaam to Muslims first just because of the wrong behaviour and attitude of others?

Rasulullah (sallallahu alaihi wasallam) said, "The one who makes salaam first is more closer to Allah Ta'ala." (Abu Dawood)

In another Hadith, Rasulullah (sallallahu alaihi wasallam) said, "The one who makes salaam first is free of pride." (Shu'abul Imaan)

In another Hadith, Rasulullah (sallallahu alaihi wasallam) said, "You will not enter Paradise until you bring Imaan, and you cannot acquire perfect Imaan until you possess mutual love. Shall I not show you a method whereby you will inculcate among yourselves mutual love? Make salaam a common practice amongst yourselves (at the time of meeting each other)." (Saheeh Muslim)

Similarly, a person once asked Rasulullah (sallallahu alaihi wasallam), "Which feature and etiquette of Islam is highly commendable and meritorious?” Rasulullah (sallallahu alaihi wasallam) replied, "Feeding the creation and greeting the people with salaam, whether you know them or not." (Saheeh Muslim)

And Allah Ta'ala (الله تعالى) knows best.