I don't think the intent was to knock evangelicals in particular, but rather anyone who comes to ones door to knock and sell something, provide information, get a donation, or anything of that nature. Where I live, I either encounter people selling magazines for various unlikely causes or people eager to convert me to another religion. I haven't seen a Fuller Brush or Elextrolux person since I was a child.
If you don't mind the initial disturbance, the least a polite person should do is take no for an answer and then move on. I don't know many people who are excited to invite them in, but there must be some or they wouldn't continue.
A church picking up members in a van to take them to services is great, but I'd assume that was prearranged or it was someone they knew.
Knocking on doors and saying I now know you're not interested in coming with me to church or anyplace else, can I take your kids with me and bring them back afterwards seems like a recipe for problems. I'm even more amazed that anyone would agree to that.