I really dislike annoying rude door knockers, and I don’t give a damn what the reason is for. Uninvited strangers that intentionally interrupt and bother me I have nothing but contempt for, regardless of the reason they’re invading my private property.
I’ve had two door-to-door salesmen trying to sell pest control services. They start their spiel and I interrupt saying “I’ve already got a service I like.”
Invariably they next ask “May I ask who you are currently using?”
Then I get rude and say “It’s none of your business” or “You don’t need to know that!”