Nothing is meaner, and more typical of the mob, than to speak in glowing terms of those whom one held in little account before their rise to eminence.

[Il n’y a rien de plus bas, et qui convienne mieux au peuple, que de parler en des termes magnifiques de ceux mêmes dont l’on pensait très modestement avant leur élévation.]

Jean de La Bruyère (1645-1696) French essayist, moralist

The Characters [Les Caractères], ch. 12 “Of Opinions [Des Jugements],” § 5 (12.5) (1688) [tr. Stewart (1970)]
    (Source)

(Source (French)). Alternate translations:

There's nothing so mean, and so like the Mob, as to talk much in the praise of those very persons, of whom we thought indifferently before their promotion.
[Bullord ed. (1696)]

There is nothing so mean and so like the Vulgar, as to talk much in praise of those very Persons, of whom we thought indifferently before their promotion.
[Curll ed. (1713)]

There's nothing so mean, and so truly vulgar, as to sound the Praise of those very Persons, of whom we thought but indifferently before their Promotion.
[Browne ed. (1752)]

There is nothing so mean and so truly vulgar as extravagantly to praise those very persons of whom we had but very indifferent opinions before their promotion.
[tr. Van Laun (1885)]