That blogpost you link to is only about corporate contributions to Free Software, which certainly doesn't constitute ALL contributions. I'd also be interested in knowing which projects they contributed to.

What exactly do you show them that convinces them?

It doesn't matter what Monty knows. All that matters is what is behind the door he opens. If it is a goat you need to switch to get a 2/3 odds for a car. It wasn't specified what happens if he opens the door with the car.