[apodildNoli]

As-salamu ´alaykum my beloved brother ghulamraza,

Some people are insensitive to other people's feelings and understanding of the Deen. You need to be compassionate with people. Just like they try to "force" their opinion on you, some people may try to force their opinions on them as well. People often think that the little knowledge that they think they have is the end-all, be-all.

While you may cite your evidences, so can the "opposition". The Shafi'i school is clear on it being a fard, and there is no salah for whoever leaves it out. And their evidences are plentiful (and authentic). Similarly they have explanations for every single "proof" that you just cited. Therefore yes, not reciting behind the Imam renders your prayer null and void - according to the school of Imam Shafi´i. You call it a minor issue, those who believe one's prayer is dependent on it would disagree.

It is good that you are zealous, just make sure it is for the right reasons. And it would be better you spent your time on more fruitful endeavours in this blessed month of Ramadan, .

wa'Llahu a'lam
May Allah bless you.

wassalam