This is my theory, which I believe to be very possible. The exos were designed as war machines. Clovis Bray forcibly wiped them from time to time to keep them more servile.
The Long Slow Whisper is Destiny's version of Order 66. The thing that will remove all free will and turn them into remorseless killing machines. This is why Cayde says this information would be very bad to certain entities if it was made public.
Probably turns them over to Rasputins control. One of the old lore cards involves R talking to the Exo Stranger and he says she's not "one of his". The old lore cards also say that the exos were created to fight some forgotten war against a forgotten enemy