“It is difficult to get a man to understand something, when his salary depends upon his not understanding it!” - Upton Sinclair
People tend to understand this as saying that people will fight you and feign ignorance. I think it should be taken more literally: a person’s financial position affects their reasoning, and it is literally difficult for them to understand something that will harm them. Not impossible by any means, but when there’s a financial incentive not to understand, it’s far more likely that people just won’t get it.
I suppose the distinction I'm making is one between bona fide self-delusion and knowing cynicism.
Everyone here is probably intimately familiar with that attitude, since it permeates software engineering (and probably every other technical field).