“Bitcoin maximalist” is a pejorative invented by Vitalik Buterin circa the Ethereum ICO. It’s best understood as a laxative for one’s disposable income, prescribed by the Ethereum doctors to be imbibed by would-be altcoin investors.

Altcoin promoters quickly attached themselves to the term for financially motivated reasons, unsurprisingly. Notably it has little to no meme/entertainment value: its value is strictly limited to psychological warfare, and is rooted in sophistry.