That's the message STeve Kelman got from SESers.
I'd draw a parallel between evaluating and firing teachers and evaluating and firing other bureaucrats. Teachers can, we assume, be evaluated based on whether their students consistently each year improve. For some bureaucrats we may be able to find similar measures of performance, but for most it's going to be difficult. For both teachers and bureaucrats you have a supervisor whose judgment is going to be invoked in the evaluation and the firing. Unfortunately, I think it's true it's harder to evaluate supervisors than it is their employees.
On a personal note, thinking back over my career I'm not at all sure how I'd evaluate myself as a supervisor: some years and with some employees I was pretty good, with some employees and other years I was poor. Rather reminds me of the director's commentary on "The Hunt for Red October" we watched last night. The director kept saying he wasn't sure whether what he had tried to do came off well.
So, bottom line: while I can agree with the message Mr. Kelman takes away, it's wise to be cautious: a bad supervisor can do a lot of damage.