I think it's a good attitude to take, particularly when dealing with peers. Giving others the benefit of the doubt and not assuming that everyone should know everything you know goes a long way toward making the world a better and more tolerable place. Also, when discussing matters of principle it's extremely valuable to be able to understand and argue for the opposition, rather than merely dismissing opposing views as 'stupid'.

However, the author is fundamentally wrong. There are stupid people. I didn't believe it until I got out of my college/career track and met a few of them.