I don't think anyone is saying they have figured out the perfect way to evaluate teachers
No, we do. You just said it in your last post. You said teachers believe we have perfect metrics for other professions. ALL other professions.
What's good for the goose is good for the gander. If there are teachers who believe other professions have perfect metrics, then there must be people from other professions who think we have or can have perfect metrics for teachers.
I said nothing of the sort. I sarcastically said they must believe that or else their argument is incredibly dishonest. I don't actually think they believe this; I think their argument is incredibly dishonest.
It is no different than saying "if you believe that then you must believe pigs fly." You don't actually think they believe pigs fly, you are making a comment about how ridiculous their other belief is.