No doubt we can and should always strive to be more charitable in our discussions. No argument there. But if the world postmodern Christians want to live in is one where we must believe that all of the contradictory things said about Jesus and his Church are equally true....well, I think you'll find that view hard to defend and even more difficult to convince people to die for.
St. Paul and all the Church Fathers and martyrs who suffered to preserve and pass down the truth had a lot of "certainty" about their beliefs. The key is they also had abundant humility; not in regards to the truth but in regards to themselves. They did not invent the truth--they simply received it and lived it and refused to make excuses for falsehood. Why? Because in the end heresy will destroy the soul just as pride will.
G. K. Chesterton, in chapter 3 of his short little masterpiece "Orthodoxy", brilliantly notes that "...what we suffer from today is humility in the wrong place. Modesty has moved from the organ of ambition. Modesty has settled upon the organ of conviction; where it was never meant to be. A man was meant to be doubtful about himself, but undoubting about the truth; this has been exactly reversed. Nowadays the part of a man that a man does assert is exactly the part he ought not to assert--himself. The part he doubts is exactly the part he ought not to doubt--the Divine Reason...."
"...Thus we should be wrong if we had said hastily that there is no humility typical of our time. The truth is that there is a real humility typical of our time; but it so happens that it is practically a more poisonous humility than the wildest prostrations of the ascetic. The old humility was a spur that prevented a man from stopping; not a nail in his boot that prevented him from going on."
"For the old humility made a man doubtful about his efforts, which might make him work harder. But the new humility makes a man doubtful about his aims, which will make him stop working altogether."