Who's stupid?

Whenever possible, I like to give my customers some props – treat them as if they were smart, cute, clever, funny, etc. But what about when I need to just patiently keep pointing out their operator errors, e.g. “It’s all set to pump, Ma’am – try pushing the start button again.” Sometimes we can’t protect them from feeling stupid. And, their sense of being called out for their stupidity does often correspond with them starting out to blame us. They have a bias towards someone being at fault - it's got to be either us or them. This gets in the way of us just collaboratively trying to fix the problem.