Buying bitcoin is a trade. The other side of that trade, someone is willing to accept USD for their BTC. It's not "burned" when you buy. The only way the USD can become deflationary is if the Fed stops printing money and banks are required to have 100% capital reserves for loans. Never happening, ever.

Inflation and Deflation are monetary tools. Bitcoin is deflationary in the sense that eventually the inflation rate will come to zero, but the inflation rate isn't zero. It will soon be less than the de-facto FED inflation target (2% in stable times). But, that's kind of meaningless. The point is, deflation CAN be a bad thing, that's up to Bitcoiners to theorize about think about, though (https://www.investopedia.com/terms/d/deflationary-spiral.asp).

Buying Bitcoin doesn't make the dollar deflationary. FED policy would. People have explanations that they use to change the rules of the tools they use. If the FED does "tapering" here because of CPI inflation--it's using the data from CPI's explanation of what inflation is and how it affects it's user base (people who use the dollar), and concluding that the best thing for it's users is to print less money. Some people think that's a mistake. Fine, at least now we have a way to make participation in that monetary system voluntary!

But, contrary to what some people on Twitter say, I think it's stupid and dangerous to over extend yourself into ANY one asset (especially Bitcoin). Like "democracy is the worst form of government – except for all the others that have been tried." The dollar is the worst stablecoin except for all the others that have been tried. But that doesn't mean stablecoins are all bad. They'e tools. Don't let "maximalist" cancel culture convince you that Bitcoin is un-critisizable--that's a good way to kill Bitcoin long term. All progress come from criticism--finding problems and solving them in creative ways. That's falliablism, that's science.

IMHO Bitcoiners on the whole don't really think that deeply outside of what the major influencers on Twitter are saying (you know who I mean). BUT, consider that the security model breaks down if the incentive for miners to mine blocks is gone (the non-subsidy fees paid per block). That's why some folks in the space are trying to find solutions (Spacechains, Statechains, Drivechains, etc that rely on proposed upgrades like OP_CTV and BIP300/301) to scale Bitcoin while at the same time filling blocks with competitive useful transactions.

What we're arguing about when we talk about "inflation" and "deflation" is security. Craving security is a form of insecurity.

People are selling dollars for bitcoin. Selling makes the price go down.

Although, globally people are fleeing from their local currency to USD (or USDT etc.), which slows down USD inflation despite of money printing. Stablecoins increase the market for dollars considerably, and we'll probably see stable-dollar take over most of the fiat world in the coming years.