Basically bitcoin removes the bank's ability to derive profit from debt and that's why they're pissed off.
Debt is never a good thing. All it does is facilitate currency flow rather than solve any problems. Inevitably a whole industry appears on the back of that facilitation (banking, finance, insurance etc).
Then why don't they just mine? They can profit off network transaction fees, and can set up value-add services on top of helping deal with bitcoin (like escrow and m-of-n transactions).
It's not as if there's no opportunity here.
When a particularly nasty seasonal-storm hits town, and somebody wins "ripped off half your roof" lottery, is everybody supposed to have cash on-hand to fix it? Or do they just get to sleep in the rain while raising cash?
Debt is necessary in a lot of places, because humans, unfortunately, generally lack the ability to predict the future.
Look at Thailand. You sleep in the rain or turn the remains of your house into a shelter whilst raising the cash. Not only that, people donate some of their cash to the less fortunate.
Only conspicuous consumption (greed) and hoarding of financial assets (by class) restricts our ability to resolve these problems. Simple kindness and social empathy goes a long way.
And yes I am a rampant socialist.