Brian Krebs did just this, visiting the local police to inform them of the potential for a swatting attack.
https://krebsonsecurity.com/2013/03/the-world-has-no-room-fo...
Then when he was later SWATted:
"One of the officers asked if it was okay to enter my house, and I said sure. Then an officer who was dressed more like a supervisor approached me and asked if I was the guy who had filed a police report about this eventuality about six months earlier."
For all we know it could have saved his life.
It says something pretty sad about American society that your assumption is that calling the Police will result in them murdering an innocent person.
If I were told the chances of me dying from jumping off a cliff were 1:1000, I still wouldn't jump that cliff.
How the police respond may be weighted too much towards a specific action, but it's important to consider this is the actual reason that SWAT teams exist.
I would definitely be interested in knowing how situations like this are handled in other countries, and the success rates involved. My suspicion is that in countries without the equivalent of SWAT some scenarios don't have an adequate response, while others that we use SWAT somewhat inappropriately for that are handled better. I suspect a less military approach is better overall, but an entire lack of that option isn't beneficial either. I don't think it's hard to argue that there's far too much police militarization in the U.S. right now.
How insane is it that you have to pre-empt SWATing now?
The only reason this is even a problem is because (too) many people know that the police is so trigger-happy these days that all it takes is say something dangerous-sounding about someone else and there's a not insignificant chance that the police will murder them.
That's how out of control the "Serve and Protect" police has gotten in the US.
Speaking to cops without a lawyer is a bad idea in many cases, but this doesn't appear to be one of them.