I will agree that people often bring their own pre-concieved ideas to the Quran. No argument there, but that includes the pre-concieved idea that it is a false book, which I believe a lot of non-religious people do. They nit-pick in order to find errors, and as a result, the first thing they find which requires a little reflection, sends them away, assuming that they've disproved the Quran.

My understanding is that Islam is a very simple faith, which people have tried to make very complex. The Quran itself explains how this happens:

"He it is Who hath revealed unto thee the Scripture wherein are clear revelations--They are the substance of the Book--and others (which are) allegorical. But those in whose hearts is doubt pursue, forsooth, that which is allegorical seeking (to cause) dissension by seeking to explain it. None knoweth its explanation save Allah. And those who are of sound instruction say: We believe therein; the whole is from our Lord; but only men of understanding really heed." (Quran 3:7)

The idea is that some people will try to control others by interpreting the Quran a particular way, and attempting to force that interpretation upon others.
This is obviously against the message of the Quran.

However, your point about the flat earth is one I've never heard before. I will do some research into that.