Managers should interfere if the rank'n'file are going off on a wild tangent with a project, but otherwise stay out of their hair. How would a non-technical manager know the difference?
How right you are.
A story going something like this: " when I came in (asked to help them with banking) there was 4 "programmers" (the manager did not know that "a" programmer is not a '51 programmer) using malloc, function pointers, RTOS float6ing point and who knows what else on the 3rd revision of the hardware (the HW designer knew that 2-4k was enough, but had to accomodate the "programmers" with first 64k, then 256k). Well, once i realized what the task was and seeing the mess, I went to the non-technical manager and told him to throw the "programmers" out and get a '51 guy (this was a "weekend emergency help" while being busy with something else). He refused stating "they are all very well qualified" to which I could only respond "to do what?". Well I have since seen the product and, yes, it works, but how much faster, better and cheaper would it not have been if done by a '51 guy in 4k and a month?"

The main purpose of mid-level managers is to provide a buffer between the troops and the clueless high-level management. High-level management decides what needs to be done. Mid-level managers keep the high-level dorks from mucking with the troops so that the technical people can get the job done. At the same time, they make sure that the troops are actually getting the job done.
said in one sentence by Buddy Norton: "the first duty of a manager is to protect his employees"

Erik

PS Buddy Norton is just a guy I once worked for. Not a public speaker or such (as far as I knew)