Rob, this phrase "monopoly on truth" is a worn out cliche. It's becoming meaningless because it ultimately represents skepticism even about ourselves. Everyone believes they have a monopoly on truth, or else they don't really believe what they're saying. Yes, Rob, even you in your above quote. Just for effect, let me throw in a little Chesterton:
At any street corner we may meet a man who utters the frantic and blasphemous statement that he may be wrong. Every day one comes across somebody who says that of course his view may not be the right one. Of course his view must be the right one, or it is not his view. We are on the road to producing a race of men too mentally modest to believe in the multiplication table. We are in danger of seeing philosophers who doubt the law of gravity as being a mere fancy of their own. Scoffers of old time were too proud to be convinced; but these are too humble to be convinced. The meek do inherit the earth; but the modern sceptics are too meek even to claim their inheritance. It is exactly this intellectual helplessness which is our second problem.And let me suggest that this same intellectual helplessness is endemic in modern Protestant Christianity today, as well. We've made a virtue out of being able to sentimentally say, "I don't really know, and that make me humble." But we're too skeptical to know whether humility is really virtuous. Either own your beliefs, Rob, or don't. But if you don't think it's true, then don't waste someone's time by saying it out loud.