Sufficient proof would be something (anything) to suggest that the outcome would have been different if the incidental element of his race was different, apart from including your conclusion as a premise by saying “Well, he was black, so it seems most probable that he was a victim of racism.”
This is hard to accept because anyone looking at the scenario dispassionately would logically expect (up until the arrest) precisely the same reaction from the bank if the customer were black, asian, white, or an inanimate carbon rod magically imbued with the ability to be responsible for financial transactions.
Mr. Njoku complains “I was embarrassed. She asked me what I did for a living. Asked me where I got the check from, looked me up and down—like ‘you just bought a house in Auburn, really?’ She didn’t believe that." Well, sure - that’s exactly what anyone would experience in that situation, if they had a parallel past history with the bank and cheque which varied in appearance from the teller’s expectation. If your finances have become significantly screwed up, get used to being treated like a bug by anyone who is looking at your records. (At least, this was my experience during the time it took to recover from a financial disaster that suddenly left me with a couple of grand in debt and no income - those bright, helpful, glad-to-see-you faces rearrange themselves into dubious expressions of thinly-veiled contempt when those red flags show up, and you bet your ass that it’s humiliating - but it ain’t racist.)
What sets this incident apart is that the bank proceeded on the belief that the cheque was a forgery. If you’ve ever worked in financial services you aren’t going to lend much credit (heh) to the notion that they invited Mr. Njoku to back into the branch and arranged to have police waiting for him based on the suspicion that the cheque was forged - this is simply not credible; if they took this step it was because they had followed rigidly-prescribed procedures for fraud detection and somehow the policies they had in place returned a false positive. Either they were directed to look for security features which were not appropriate for the instrument in front of them, or there was a transcription or MCR error when they attempted to confirm the validity of the cheque.
To characterize this as a mere “alternate” explanation for what happened, on parity with “they must have assumed it was fraud because he was black” is not a reasonable position. The “non-racist” explanation is consistent with the facts as presented. To argue this way is to put yourself in the same category with people who argue that creationism is just a good a theory as evolution. No, it’s not - if you have an extraordinary position, you’d better have some strong evidence to support it.
This is not nearly the same thing as saying that racism doesn’t persist into present day, and anyone who capable of thinking that clearly spends their days in Cloud-Cuckoo Land. However, this outcome is completely explicable absent racism, as a result of (entirely reasonable and predictable) scrutiny and an honest procedural error. This conclusion is supported by the general outcome in situations like this. If Chase’s policies and culture allowed for the possibility of clients being arrested on mere suspicion of fraud, then we would expect to hear stories like more frequently.
Bank employees are basically automatons, and they are carrying out policies which are designed to be of maximum benefit to the bank. It doesn’t serve the bottom line to alienate 30% of their potential clients, so you can bet your ass that they have fastidiously crafted their policies to be anti-racist. Really, a bank only cares about the colour of your money.