It doesn't matter who finds it acceptable or not -- loan rates are determined by a market, and there's very little demand for opening new longs. Apparently there are enough people who prefer to offer their USD at these low rates over pulling the USD out of BFX.
BFX has historically offered great interest rates on USD. If you have a lot of USD there and you expect rates to rise at some point in the near future then it makes sense to leave the money at BFX - and 0.02%/day (which people fill on the demand side now) is more than 0%/day, right?
As you say, interest rates are set by demand and supply. Right now it's the bearmarket and the swap demand has clearly shifted towards BTC.
BTC loans are at record highs http://www.bfxdata.com/combined/btc.php
What that guy who decided to sell 1600 BTC short at $469/$470 today was thinking is a rather interesting question - but I guess it's great risk/reward if you see the $200 in the cards..
I know it appears a bit sad and depressing that USD rates are this low right now. We who have been using BFX for quite a while remember the good-old-days of 0.99%/day and miss them. However.. we won't be seeing those rates again. Back when 5 people were using BFX it was possible to get those rates like that but the user-base at BFX has grown a whole lot and there are a whole lot of people who think 0.2% or just 0.1%/day is GREAT (and it is, when you think about it, pretty darn good compared to many alternatives).
What they sadly won't do though is increasing the dollar swap rate. Hopefully we have bottomed out by now. Anything below 10 % pa will give me some serious headache.