I have just learned to tell people "No" and when they ask "why not" I just answer "Because. Now go away."
The more you try to comply or explain the worse it always goes for you because they are looking to make trouble.
I recently tried a novel approach with some Jehovah’s witnesses who appeared at the end of the driveway while I was walking the dog.
They got out of their car and got about three words out....
I stared at them and started pointing and screaming:
“Look at your eyes. Look at your eyes. You are brainwashed. Get out of here.”
They stopped talking but did not retreat back to their car.
I repeated my mantra.
They ran back to their car and drove off....