Agreed. When you have a really hard programming task, you need to be in problem-solving mode, and a lot of times you have to find errors in your own thinking. A big ego will only limit your capabilities to find misconceptions you hold true.

A big ego might help to project an image of how cool you are, but computers couldn't care less.

It also explains -in my opinion- why geeks are not the aggressive type. It's just a waste of energy when you're dealing with a computer.