Baltasar Gracian's Aphorism 197: Do not saddle yourself with fools. "He is one who does not know them, and a greater, he who knowing them, does not shake them off, for they are dangerous in the daily round, and deadly as confidants, even if at times their cowardice retrains them; or the watchful eye of another; in the end they commit some foolishness, or speak it, which if they tarry over it, is only to make it worse: slight aid to another’s reputation, he who has none himself; they are full of woes, the welts of their follies, and they trade in the one for the other; but this about them is not so bad, that even though the wise are of no service to them, they are of much service to the wise, either as example, or as warning."
My interpretation: You may tolerate a fool for many reasons that can be or can seem valid: politeness, business, a mutual friend, weariness, mistaken benevolence, a public situation... But there is no reason to allow a fool to come into intimate circles or your confidence. Fools are like the malicious; they inflict damage on your life. The damage may be unintentional but that does not make it less severe If you do not protect yourself from the damage fools can inflict through their reckless disregard for prudence and propriety, then protect those around you because the damage will spread to them as well. An ill-occasioned confidence can harm everyone who is affected by it and the confidence will be used in a salacious manner, like a sordid social currency, with no regard for the innocent.