Henry Ward Beecher (1813-1887), "Men Need What They Do Not Want," in Eyes and Ears
(Boston: Ticknor and Fields, 1862), pp. 161-164 (at 161):
Men love to read "on their own side," to hear the things which they already believe enforced with new arguments; to hear their ministers or political speakers praise the things in which already they are fully established. But they are seldom willing to hear another side, to have enforced the truths which they do not believe, and the qualities which they do not possess. In this way men grow narrow: they intensify their opinions, rather than enlarge their knowledge, and become selfish and bigoted.
Id. (p. 162):
Men strengthen each other in their faults. Those who are alike associate together, repeat the things which all believe, defend and stimulate their common faults of disposition, and each one receives from the others a reflection of his own egotism.