In their prime, the baby boomers had pretty handily ruined the economy and the environment, leaving millennials to clean up their mess and become the first generation in American history with a lower quality of life than their parents. When millennials and Gen Z-ers couldn't afford various luxury industries that previous generations took for granted, (white) baby boomers blamed them for "killing" or "murdering" said industries. When millennials and Gen Z-ers complained about the circumstances forced on them and proposed political or economic solutions, (white) baby boomers mocked them for being "lazy", "entitled", and the personal favorite of many, "snowflakes". This last was literally one of the stupidest insults in the English-speaking world. Anyone who said it unironically sounded like a five year old calling his sister random words because he didn't understand how insults work.
This is not to say, of course, that millennials as individuals or as a group were without flaw, but the negative stereotypes leveled at them were for the most part unfair and unwarranted. One day, millennials decided they'd taken enough abuse and started responding to baby boomers' bullcrap with a sarcastic and condescending "OK boomer." There was nothing particularly clever about this phrase, but it became wildly popular because of its surprising effectiveness at offending the very same (white) people who had been mocking them for being easily offended. One boomer, a (white) conservative radio host, was so offended that he published a very stupid Tweet, which in fairness was less stupid than almost every Tweet written by the President of the United States at that time, but was still very stupid.
Were baby boomers legally bought and sold by millennials who took them from their homes in obscenely crowded ships, forced them to perform arduous manual labor, beat them with no repercussions, and had complete control over their lives, for hundreds of years?
Did evangelical Christians ever develop an almost universally accepted theology claiming that baby boomers were cursed by God because of their lineage, and therefore fundamentally inferior to millennials?
Did scientists ever develop almost universally accepted hypotheses claiming that baby boomers were biologically more primitive and less intelligent than millennials?
Were baby boomers at one time classified as three-fifths of a person by the U.S. government?
Have baby boomers ever been burned, shot or lynched because of their age or the year they were born?
Did eugenicists like Margaret Sanger regard baby boomers as an "undesirable" population and leave a legacy that would continue to systematically target their communities up to the present day?
Did the Home Owner's Loan Corporation ever label neighborhoods with high percentages of baby boomers as "risky investments" that would subsequently be denied mortgage loans for decades?
Have baby boomers ever been denied access to public pools, clubs, restaurants, theaters, libraries, hotels, etc. that were open to younger people?
Have baby boomers ever been forced to sit at the back of public transportation because of their age or the year they were born?
Did baby boomers ever have to use separate water fountains from millennials?
Is a job application with an "old" sounding name demonstrably less likely to be accepted than the exact same application with a "young" sounding name?
Do baby boomers disproporationately get pulled over while driving compared to millennials?
Are baby boomers disproportionately targeted and incarcerated for drug offenses and other non-violent crimes that millennials are far more likely to get away with?
Are baby boomers regularly murdered by millennial police officers with little or no provocation?
Do millennial supremacists march in American streets with few if any repercussions?
I notice that you had no problem spelling out "Boomer", yet only referred to the n-word as "the n-word". Is this because you actually know fine well that the latter word is much, much more offensive than the former, for very obvious reasons, and that only a complete imbecile could fail to recognize this?
The Tweet was eventually deleted with no explanation or apology, but it would forever be immortalized as yet another piece of our species' sad history, and the first organized retaliatory strike by millennials in a war that they sure as crap didn't start.