I'm just a dabbler, but it strikes me that a brain evolved to ignore reality would not have survived.  Our biases must at least leverage off the real world.  There must be some limits, some checks.  Maybe that's why we operate one until we get "a wakeup call" leading us in another direction.
Our biases are towards a "group think" mentality, which I agree has "real world" self-reinforcing traits -- you might get kicked out of the clan for "out of the box" thinking (especially if results are bad).

I'm interested in how to get around this cloistered behaviour -- how to get people to think independently.

I've always thought that some people (especially the John Wayne American icon image) think of themselves as individualists, without seeing the socal context that individualism is rooted in.

That said, I bet there is some variation between us all, just because a 'mix' is better for the survival of the rest of our genes.  There is no advantage in the children on one set of parents being uniform in this, or any other heritable trait.