The proliferation of digital money is undesirable for banks, given their current problems they have been facing recently. This, first of all, is about the low demand for loans, lower profits due to reduced interest rates and fading hopes for deregulation.
I see a point here, but i think that is more of a problem between bank competitions. Bitcoin does not offer any loans, in fact owning bitcoins and keeping them in your wallet does not earn you interests, instead we are merely hopeful that the price will increase and that we hit the jackpot. Perhaps the only threat bitcoin pose as of now is the amount investors chose to put into bitcoin instead of the banks, but trust me, there are still many out there that views bank as better options rather than bitcoin.