Intellectual arrogance seems to be a common failing of developers. You're not as smart as you think you are, nor are other people as stupid.

You may have very different definition of what stupid means then I do. For me, for example if somebody does something immoral, or tries to cut corners when they shouldn't this looks incredibly stupid and is ground for termination. Very clever people can be incredibly stupid in their actions, and thus be stupid, by my definition.

It's not about me being smart. It's about being able to recognize stupidity.

I'm not saying you should avoid stupid people because they are worse than you. I'm sayin you should avoid them because stupid actions have surprising consequences and you don't want to be caught in that.

You see somebody thinking it's ok to keep passwords in clear text? To keep random people's data without very good reason? To screw their business partners? To romance their employees? To not repay their due debts as soon as it's possible? That person is stupid even if they have iq of 200.