One half of the world laughs at the other, and fools are they all.

[La mitad del mundo se está riendo de la otra mitad, con necedad de todos.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 101 (1647) [tr. Jacobs (1892)]
    (Source)

(Source (Spanish)). Alternate translations:

One part of the world laughs at the other, and both laugh at their common folly.
[Flescher ed. (1685)]

Half the world laughs at the other half, even though the lot are fools.
[tr. Fischer (1937)]

Half the world is laughing at the other half, and folly rules over all.
[tr. Maurer (1992)]