If anything this will be used as a tool to drop bitcoin price so the wealthy can get a deal at the expense of retail...
Who do you think are selling?Institutions got in between 5-10k and when it gets too risky then they are the first to sell. That's just how it is.
Is the fear that Bitcoin is only being propped up by USDT? If that's true, and USDT explodes, why would BTC price necessarily go down with it? The theory is that USDT has propped up Bitcoin enough for it to be the new equilibrium price.
The price would fall because several exchanges and Tether bought Bitcoin for free. People would get scared and sell - liquidity will take a heavy hit (Tether provides a really high percentage of liquidity). High buy orders would get bought up/cancelled fast, people who hold Tether cannot exchange it to anything anymore.