The part that's right: some of the people banks employ are absolutely willing to make a dollar no matter what it takes, and they will happily look the other way when suspicious activity is pointed out to them. I found this attitude particularly prevalent among some of the salespeople.
The part that's wrong: these are not mostly easy or obvious decisions. Banks don't just know that a transaction is indicative of illegal activity. A regular part of my job was debating with my coworkers about whether we should be concerned by some transactional pattern. More than once I followed bank policy and flagged activity conducted by wealthy people that turned out to be completely legal. The reality is that while some cases are cut and dry, most of them fall into some grey area and require thoughtful judgment.
What makes it even worse is that preventing transactions may not even be the best course of action when suspicious activity is identified. A classic example is Paul Manafort's activity with the Bank of Cyprus. BoC compliance officers questioned Manafort about some of his activity, at which point he immediately stopped transacting through the bank. This is obviously anathema to law enforcement, who would prefer not to alert their targets.
All of this is to say: AML policy in the U.S. is a big mess, and even though it's meaningful work, I'm glad I got out of it. Until there is some kind of rational regime, bank officers are damned if they do and damned if they don't.