I'm not sure I understand the adversarial part or why that should matter. He mentioned it being a zero-sum game, with some having to lose for others to win. I don't get why that's relevant to the programming language choice.

I think what he should have said is that financial transactions are important, and that it's expensive to screw up. This is of course as true or more for, say, NASA's flight software (which is not problem that's not adversarial in the way he means) as it is for financial trading software.