This was actually pretty mild as JW medical misunderstandings go.
The JW organization at one time claimed that vaccination violated Biblical prohibitions against bestiality based on the mistaken notion that heredity was in the blood.
The current ban of transfusion medicine was born as a direct result of the mistaken belief that blood itself is the food upon which our bodies are sustained instead of simply the transport medium.
They claimed that predilections towards murder and other forms of violence could be transmitted by a blood transfusion
They claimed that organ transplantation constituted cannibalism.
They claimed that an organ transplant could result in a "Personality transplant" as well.
If you go even farther back into the 1930's and 1940's it gets even worse.
I would suspect that most active JW's would say, "Yes that is embarassing, but those views were not really spiritual in nature and don't affect my relationship with Jehovah. Besides, these are imperfect men who weren't inspired."
I would agree up to the point where innocent people get harmed. When these views cause real, lasting harm I would say that anybody that was a party to teaching those views could potentially bear some responsibility. (Depending upon the extent to which they were themselves hoodwinked) --And that would affect your relationship with God.