They may agree with your contentions about the positive nature of Islam. But, in the same breath, they will say - "Ah! But you are the same Muslims who marry more than one woman. You are the same people who subjugate women by keeping them behind the veil. You are fundamentalists, etc."

I personally prefer asking the non-Muslim upfront, what he feels is wrong in Islam. I prefer asking directly, what they feel is wrong in Islam with their limited knowledge, whether right or wrong and from whichever source it may be. I encourage them to be very frank and open and convince them that I can take criticism about Islam.

In the past few years of my Daawah experience, I have realized that there are barely twenty most common questions that a common non-Muslim has regarding Islam. Whenever you ask a non-Muslim, "what do you feel is wrong with Islam?", he poses five or six questions, and these questions invariably fall among the twenty most common questions.