Prejudice in favour of one’s own country, combined with national pride, makes us forget that reason is found in every land, and sound thoughts wherever there are men. We should not like to be thus treated by those whom we call barbarians; and if we ourselves display a certain barbarism, this consists in being panic-stricken at seeing men of another nation reason as we do ourselves.

[La prévention du pays, jointe à l’orgueil de la nation, nous fait oublier que la raison est de tous les climats, et que l’on pense juste partout où il y a des hommes. Nous n’aimerions pas à être traités ainsi de ceux que nous appelons barbares; et s’il y a en nous quelque barbarie, elle consiste à être épouvantés de voir d’autres peuples raisonner comme nous.]

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

The Characters [Les Caractères], ch. 12 “Of Opinions [Des Jugements],” § 22 (12.22) (1688) [tr. Stewart (1970)]
    (Source)

(Source (French)). Alternate translations:

Our prepossession in favour of our Country, join'd to the pride of our Nation, makes us forget that Reason belongs to all Climates, and just Thoughts to all places where there are Men. We should not like to be so treated by those we call Barbarians; if amongst us there is any barbarity, it is in being amaz'd at the hearing other People reason like our selves.
[Curll ed. (1713)]

Our Prepossession in the Favour of our Country, joined to a national Pride, makes us forget that Reason is the Growth of all Climates, and that a Justness of Sentiment is not limited to a Part of Europe: It would enrage us to be so treated by those whom we are pleased to call Barbarians; if amongst us there is any Barbarism, 'tis in being amazed at hearing other People reason like ourselves.
[Browne ed. (1752)]

Our prepossession in favour of our native country and our national pride makes us forget that common sense is found in all climates, and correctness of thought wherever there are men. We should not like to be so treated by those we call barbarians; and if some barbarity still exists amongst us, it is in being amazed on hearing natives of other countries reason like ourselves.
[tr. Van Laun (1885)]