How can the banks corrupt bitcoin exactly?
by offering something similar, that in apparance may look more secure, and decive average joe, it's all about getting those "average joe" to use your service
until now it's bitcoin that need to "corrupt" fiat and steal their "customers" in order to succeed, banks can hinder this in the future
average joe's always accept the products that banks offer them, even though they are quite expensive. something great as bitcoin can save them a lot money and hassle, only they think it's not safe and don't think it's worth it as they don't know what bitcoin exactly is.