I don’t think banks are the ones against Bitcoin. It should be the government that is against Bitcoin because they don’t have control over it. The banks actually report to the government and because Bitcoin isn’t doing the same, they don’t like it. Because starting from tax and other things they’d have implemented or rule they’d have set, they can’t. Bitcoin takes out the middle man and the government can’t do nothing about it, no matter much they dislike it.
The question is s, who's the bank and who's the government? They are same set of people under the financial system and their interest, policies and objective are twined. The banks are more like an agents of the government through which the government can use to bar and frustrate any other rising financial system that tend to be of a treat to their power of control and bitcoin is one of such with it's decentralized protocol. Which makes puts me in the right by referring the bank as a middle too.
Nonetheless the bank and the government are not the same. Understand the difference that the bank is not owned by the government. There are many private owner and they don’t have any personality in the government. However, the government under policies use the bank to do and get whatever they want. And that’s because banks follow policies which are set by the government. So government may use the bank as a tool but they are not one.
Please correct me if I'm wrong. As far as I know, there are many private banks, but in order to operate, they must go through and be managed by the central bank, and the central bank is directly managed by the government. So it can be said that the person behind the bank is the government. To me, banks are one of many tools that governments use to maintain the economy and control their people.
Answering OP's question, I never thought that banks or governments were against bitcoin, the role of banks in the world economy is extremely important and no one can replace it, including bitcoins. We don't need to exaggerate bitcoin and there are always hostile thoughts about why banks and governments are against bitcoin. If governments and banks against it, why are more and more countries legalizing bitcoin and bitcoin gradually becoming more popular?