Groupthink has been around since the first Craftsmen's Guilds (ca. 200 BC or earlier). It's just that "Groupthink" was not always known as such. Back then, it was likely called, "Adhering to Standards" or something similar.
When everyone in a guild or corporation has the same values and similar reasoning skills, then it is more likely that the guild or corporation will produce goods and services of consistently high quality.
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No love for Hamas, Hezbollah, Iranian Leadership, Islamic Jihad, other Islamic terrorist groups, OR their supporters and sympathizers.