Two points come to mind:
1) If we assume the monetary system is a closed system, i.e. no new money printed/destroyed, then money can only be transferred. The legal transfer of money only has two requirements--the transfer must follow existing laws and the transfer must occur among two or more willing parties. There is no such notion as "extractive economy." Transfers of money for no exchange of goods or services happen every day--birthday/anniversary/Christmas gifts (I didn't trade the money for the goods. I just got the gift.); inheritances (I didn't work for the assets. I just had a rich uncle.); social services/EIC/gov't cell phones (I didn't earn my rent/food/medical/cash/phone subsidy. I just don't earn enough to disqualify myself.).
From my work with fraud investigation groups in financial industries, I know that much effort and resources are spent addressing illegalities (fraud, money laundering, identity theft) and compliance (RICO investigations, SARs, SEC/tax compliance). Churning is just part of the cost of doing business. Management is usually more interested in whether a campaign is legal and profitable. If it's legal and the profits meet expectations, the minor details of "how" pales in comparison to "how much."
Finally, I look at this as arbitrage situation across monetary mediums. For hundreds of years, businesses have spent much effort to make money in currency exchange. Believe me, if a bank's computer can find 30 seconds of currency arbitrage in global markets or exchanges, it will exploit that opportunity if possible to turn a profit. This is simply a bank taking advantage of a market inefficiency. This is not unethical whether banks or people do it in my opinion.