Voltaire attacked the ideology and not seeing "reality as it truly is" for humans love motivated reasoning and giving long speeches [smiles at Mookie in the background at the irony here.]. So in one of his satirical works called "Candide, ou l'Optimisme / Candide: or, All for the Best (1759); Candide: or, The Optimist" ...

In this satirical work Voltaire critique Leibniz's Optimism [Gottfried Wilhelm Leibniz the calculus guy, also was a philosophical guy who believed we must be living in the best of all possible worlds, for God made this world , God is good, something something this world must be necessary in some way to solve the problem of evil.]

In Candide the main character after suffering hell, but other states of mind and social spaces constructed by man, after suffering other things that were not hell, and thus having a mixture of reversal of fortunes half a dozen times. Well he is lectured to [once again] by his mentor Professor Pangloss.

Pangloss once again in very earnest insistence that all turned out for the best by "necessity" (aka God), so Candide responds

"That is very well put . . . but we must cultivate our garden.” [aka Voltaire's version of "ok boomer."]

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The whole point of Ok Boomer both the original meme on tik tok and the derivative forms is we can use language to alienate people. To say ones suffering is necessary for "it follows some grand plan, or that is the way things are."

This is a form of "bad faith," and you are treating other people's pain like they are an object and not a subject. It is a perfectly normal and rational response to say FUCK YOU, and then end the conversation with the person who is lecturing you. "Ok Boomer" is such a form of middle finger.

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Yes it is crude, yes it is obnoxious, but you have to understand the preceding act is obnoxious and crude as well. You are just responding in kind.

And of course this will annoy the older people, this will annoy the people who have more power, for part of how "hierarchy works" is the people with more power in the social totem poll expect civility from their "lessers" on the totem poll.

But when someone treats another person as an object, flicking them off, giving them finger, is a natural response.

[And yes this is way too many words, and thus deliciously ironic nothing is new under the sun and sometimes we linger on what is delicious. ]

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So Random Thoughts you are correct it is a term of derision and a person is emotionally offended, but I will argue it goes both ways when it is used, an act and a reaction to said act. Nonsense and thus counter nonsense (Ok Boomer is also nonsense but it is usually counter-nonsense, gibberish in response to nonsense.)