"So much for the safety aspect."

Yep.

Now why do you think AMA would want to discourage the turbine?

In my mind, I relate it to why airline company management hates the Captains so much. Management hates the Captains and thus the entire pilot groups because once that airplane pushes off the gate, the Captain is the sole COMMANDER (real captains that is) and no one can do anything about it. The company has NO control over him. He is 101% autonomous. He will make more life-decisions in one flight than the company CEO can dream of in a life-time.
That is the answer: CONTROL. AMA wants to establish ultimate CONTROL and of course the script answer is insurance. Bah Humbug. It's CONTROL.