That's precisely how you would keep a peg: let the market enforce it and bear the brunt of the speculative action, then intervene brutally to restore the peg and reward those who held the line with profits. If you do it a few times, nobody will bet against the peg ever again.

Of course, this is all predicated on you actually having the massive assets required to fight a speculative market. That shouldn't be a problem for something like USDT which should be backed 1:1. So let's sit back and enjoy some price discovery (though I wouldn't be caught dead in USDT).