For a while here in AZ, there was a rash of home invasions where they would have one person who looked nonthreatening knock on the door. When the homeowner felt comfortable and would start to open the door, they would bum rush the homeowner and enter the home to rob, etc. I look through the peep hole and then go back to what I was doing. I used to have a door mat (given to me by my brother who recently lost his wife to cancer) that said GO AWAY. Loved that door mat.

I suggest if you must say something, to tell them to Go away Jehovah Witnessess, if you come back I will sue you for harrassment.