“We mistakenly equate flattery to friendship and criticism to opposition; one should evaluate truth first and then judge, for flattery and criticism are primarily opinion.”
1975
Related quotes
Source: The Frontiers of Meaning: Three Informal Lectures on Music (1994), Ch. 1 : The Frontiers of Nonsense

“None are more taken in by flattery than the proud, who wish to be the first and are not.”

“Nothing in this world is harder than speaking the truth, nothing easier than flattery.”
Crime and Punishment (1866)

10 August 1749
Letters to His Son on the Art of Becoming a Man of the World and a Gentleman (1774)

Criticism
The Note-Books of Samuel Butler (1912), Part VII - On the Making of Music, Pictures, and Books

Source: Das Ressentiment im Aufbau der Moralen (1912), L. Coser, trans. (1973), pp. 67-68