for starters, what authority does the US Commodity Futures Trading Commission have over Tether and Bitfinex? 

very little. 

There seems to be enough smoke around tether to suggest something is amiss - but it is a completely seperate currency to bitcoin - and whilst it's crash might create a bit of initial FUD and bring the prices down somewhat, it doesn't change any of the fundamentals behind bitcoin, or any other cryptocurrency for that matter. 

I would argue against it creating liquidity in bitcoin, because if USDT wasn't around people would find another safe haven, whether that be fiat, or one of the other 1400 cryptocurrencies. 

in the end of the day USD is a currency that has depreciated against bitcoin for 9 years, so it's hardly a safe haven, even if many interpret it to be so.