I suppose there is no way to exaggerate how Christians are opinionated; but this piece by Isaac Watts illustrates it well.
"So good an opinion have we of our own sentiments and practices, that it is very difficult to believe what the reprover says of our conduct: and we are as ready to assent to all the language of flattery. We set up our own opinions in religion and philosophy as the tests of orthodoxy and truth; and we are prone to judge every practice of other men either a duty or a crime, which we think would be a crime or a duty in us, though their circumstances are vastly different from our own.
This humor prevails sometimes to such a degree, that we would make our own taste and inclination the standard by which to judge of every dish of meat that is set upon the table, every book in a library, every employment, study, and business of life, as well as every recreation.
It is from this evil principle of setting up self for a model what other men ought to be, that the anti-christian spirit of imposition and persecution had its origin: though there was no more reason for it than there was for the practice of that tyrant, who having a bed fit for his own size, was reported to stretch men of low stature upon the rack, till they were drawn out to the length of his bed; and some add also, that he cut off the legs of any whom he found too long for it.
It is also from a principle near akin to this, that we pervert and strain the writings of many venerable authors, and especially the sacred books of Scripture, to make them speak our own sense. Through the influence which our own schemes, or hypotheses have upon the mind, we sometimes become so sharp-sighted as to find these schemes in those places of Scripture where the holy writers never thought of them, nor the Holy Spirit intended them."