music

Popular usage changed the meaning of that word from a medical description, to a casual invective, to a slur.

Popular usage exaggerates the meaning from a mild medical descriptive to a slur. But the original meaning was couched within the language of eugenics, and was already a basis for cruel and clumsy medical policy. What ultimately changed was the explicit terminology applied to populations for the purpose of segregating, sterilizing, and exterminating whole populations. All that was left over was a school yard taunt that echoed the policies of a prior generation.

You can see charities and such from the 1960s dedicated to helping "r word" children.

Certainly fundraising off of it.

However, in the modern moment, what we've seen has been a shift from using the r-word to bandying about the terms "autism" and "Aspergers". These are fundamentally descriptions for overlapping conditions and their invective forms are even more broad based - intended to belittle any form of neurodivergence or social maladaption.

But this is exactly why scolding people for incorrect usage is often necessary. Confusing the terminology forces it out of proper usage and occludes the history that made the phrasing so dangerous to begin with. Its very difficult to even discuss historical eugenic policy (much less attempts to revive it in the modern era under euphemistic language), much less why it was such an abysmal methodology and why serious academics and activists discourage people from backwards attempts to categorize people in the modern day, if we have to constantly re-establish the definition of old words. Or, even worse, dodge censors whenever we cite historical works.

To bring all this back to "boomer", losing sight of the root terminology means losing sight of the socio-economic history around the term. The whole reason for the casual "OK, Boomer" retort stemmed from the enormous volume of mass media geared towards vilifying GenX and Millennials for failing to achieve economic roadmarks common to the prior generation.

It wasn't just "Lolz, taste in music" or generic commentary on age. It was an entire zeitgeist being contrasted with the current moment.