That's a strawman you've skewered twice already, well done.
What we're saying is: a lot of the low level infrastructure used now in finance (brokers! Dealers! Clearinghouses!) is easily replaced by some code, once you have trustless decentralized computers. Which we do now.
Then your oil barrel market is just some code nobody needs to trust, and yes, the "last mile" of it still needs "guys with guns" infra. So what? We made a part of that market freer and fairer.
Cool, isn't it?