That research was oriented towards making sure it wasn't possible though.
You're saying "of course it isn't" - but how do you know that?
At the time the Soviets had the same sort of projects. So until you're sure it's not possible, the potential capability is an enormous threat if it is.
How they went about that research is where the waste creeps in.
> General Brown: So they started doing psy-research because they thought we were doing psy-research, when in fact we weren't doing psy-research?
> Brigadier General Dean Hopgood: Yes sir. But now that they are doing psy-research, we're gonna have to do psy-research, sir. We can't afford to have the Russian's leading the field in the paranormal.
Source: The Men Who Stare at Goats
Plenty of things we could be wasting money on if the only criteria is "how do you know it's not real?", why stop at killing goats with mind bullets? We could be looking for yetis or Atlantis or lunar nazi spaceships.
It was a giant waste of time and money and, this being the CIA, it likely harmed many people.