I am not surprised by your source of information and a feeling of hatered. I see you no different from the angry Mullahs and the "Terrorist. But I will try to answer your hypothetical situation...
As an example, lets consider our own country. Hindus are the majority. And IF we had a Hindu rule and if Hindu Law/beflief required ALL Hindus (Earning a specific minimum salary with a minimum savings)to pay "Zakat". Remember, Zakat is not voluntary. It is obligatory on an individual having a certain amount of money.
In that situation, it is FAIR to TAX the non-Hindus as they are not making any contribution to society as the Hindus are through Zakat.
Again, it is an administrative tool. Think about it, if we all in India pay "TAXES" voluntarily, do we need a TAX system.
