The author basically argues that since banks take federal money or subsidies (e.g. in the form of FDIC and bailouts), they fall under Title VI of the Civil Rights Act, which prohibits discrimination by organizations taking federal money. Thus Congress should stop the banks from discriminating based on political speech.
I think it's laughable to expect Congress to do anything about it. In fact, they're probably one of the biggest beneficiaries of bank discrimination, as they can leverage their political power to help "unbank" or "rebank" their political friends/foes.
The best solution to bank discrimination is one that people on SN already know much about :)