Re: What is your argument against secularism?
I go with AH on this topic:) He is right about Pakistan was founded by Quaid-e-Azam keeping in view secular setup. As OP said, relegion should be separated from government because of mixed population with different ethinic, religious and cultural backgrounds. At present mostly successful governments of the world are secular including our neighbour India.
Once upon a time an usurper tried to impose such Islamic laws which were backfired even during his life time. Unfortunately the hotch potch Islamic system he left only created miseries and deaths to Pakistanis which is still continuing in the name of Taliban and other jehadi setups.