Laudator Temporis Acti

Samuel Butler, Characters and Passages from Note-Books, ed. A.R. Waller (Cambridge: Cambridge University Press, 1908), p. 291:

They that endeavor to redeeme the world from Error and Imposture, have a very ungrateful Imployment, for if they do any man good it is against his will, and therefore they must not only reward but thanke themselves: For as Mad men always hate their Physitians, the People can never endure those, that seeke to recover them from their deare Dotage.

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Update, from an email:

Somewhere in the Diatribes Epictetus tells of an incident that happened when he was a young philosopher still living in Rome. Full of his Stoic principles, Epictetus decided to go the Forum and socratize with some Roman senators about truth and justice. After a few minutes of engaging in elechus with the young philosopher and having what they believed in questioned, then Romans grabbed the smart aleck young philo and started slapping him. Epictetus escaped, battered and enlightened about the perils of trying to "improve" others who do not wish to be improved.

In our younger days, many of us tried to redeem the world from error. The results were predictable and the costs high. Too late we learned that the world is not worth redeeming.