Question: Who's more closed-minded, atheists or theists, and why? (And yes, this is a generalization).
Well, first I think we need to define "closed-minded".
Christians are accused of being closed-minded because instead of accepting many theories and beliefs as true, we choose to keep to one Truth.
Many who claim to be "open-minded" believe that Truth is relative. Actually, I'm not even sure they believe in any truth at all, for unless it's inclusive, they're not willing to believe it. But in everything, there has to be an absolute Truth. So technically speaking, those who aren't willing to believe in the One Absolute Truth, those who claim to be "open-minded", are actually closed-minded, for they refuse to believe that which is true.
To say something is true means that something has to be false (or untrue). But to say that there's no truth is to say that everything is actually untrue, or false. So those who claim to be "open-minded", who say they believe everything, can't be "open-minded", for they refuse to believe that one Truth exists.
Also, to say that something is false or a matter of opinion means that something has to be true or fact. That one thing that's true and fact is what we Christians stand on. Does that mean we Christians are more closed-minded?