Mercenaries at the Door

This is based on a true story. Once while tracting, a voice behind the door asked who we were. My companion explained that we were missionaries, at which point the door flung open and the homeowner asked, "who did you say you were?" Once we again explained who we were, she said "oh, I thought you said mercenaries" and then promptly shut the door again.

We figured we were fortunate to get away from the house. What kind of people open their doors to mercenaries but shut them for missionaries?