So it's OK to believe the earth is flat? Sure, it's OK, but they shouldn't expect to not have their intelligence questioned.
I can't fault someone for believing in a vague higher power. But the specificity of faith that god wants x,y, z, and has done acts a,b, c instead of d, e, or the dreaded f, seems a bit much.
One can say that it is just faith, and a personal belief. However this isn't liking the color blue versus red; true religious belief is a lot deeper than just an opinion because it pervades everything. Birth, death, marriage, celebrations, ethics, the whole bit for many is tied down to 'simple faith'. It's worth debating, questioning, and needling because it plays a huge role in our world.