I think the issue for many people (including many Christians) is the ignorance of an awful lot (majority?) of Christians, particularly in the United States. They are not only willfully ignorant of other people's beliefs, many are shockingly misinformed about their own views, as well. And they have real political influence that has many implications for public policy, the treatment of minority groups, etc.-which can't be said for most non-Christians, at least in the US. Although perhaps this is a really America-centric (and thus, hopelessly provincial) view of Christianity vs. "everything else."
Furthermore, there's a significant disconnect between someone like Augustine or whomever and how most Christians actually understand themselves. Most people aren't nearly so highbrow in their views, in general. You can argue whether that is good or bad, or value-neutral, but that doesn't change the fact that most people simply don't operate like eminent theologians or philosophers.