Umm.. that's kinda my point. JWs don't care much about this teaching - and yet it's harming the image of the organization. That makes it a "costly" teaching which is earning them very little or no returns.
What an astonishing line of reasoning, Island Man! Evidence please?
I would have thought that JW organization's image has been monumentally far, far more harmed by the fallout from its policy and practices in responding to allegations of child sexual abuse than from some obscure teaching whose greatest claim to criticism is its oddity.
I have searched google far and wide and I cannot find any evidence that JW organization's teaching on Michael as Archangel has "harmed" its image in any way whatsoever - unless you mean because some non-JW critics have questioned it (and that's hardly harming its image).