BTC has a fixed amount and the price varied on the demand and supply in the market cap. Once the demand will increase, it means the supply becomes less which in turn to BTC becomes expensive and the price was pegged into a dollar-based value. Nevertheless, it is impossible that you mean BTC will become stable in price, the price will always be fluctuated due to massive traders of altcoins in BTC pairs.
Actually right but he was trying to think of a way which can make fluctuations smaller like limiting the maximum drop/rise a day to $500 but obviously we cannot do it because you can't stop buyers from buying and you cannot force sellers into holding. But to solve the same problem stable-coins were made to eliminate these risks and if you are a merchant you might actually want to accept altcoins like TRX because BTC payments will take hours and transaction fees also hurts. I am only suggesting TRX because it has free of cost transactions and quick confirmations and the price for TRX never dropped or jumped too much either.
By the way there are merchants like bitrefill who accept bitcoins payment but how they manage price fluctuations is by constantly updating price of the cart items every 10 mins when you are on the payment page. Like if you had $10 amazon gift card and move to checkout then the price will be fixed for 10-15 mins and then update according to the market price.