Reading this it reminds me of one time a friend invited some bible people in to our new house, at that time we only had 1 chair.
Anyway they came in sat on the floor we had a debate on religion, they where respectful and polite and left when asked, before they left they insisted on saying a prayer.
They preyed and asked the lord to find us some furniture, and no word of a lie, in the morning in the front garden there was a settee and 2 chairs.
It turned out a frend had dropped them off as he heard we needed some, but still made me think.
They did return once more but when told we are not really into all that they left and never returned.
I agree though they shouldnt really go 'called calling' as there are some vunrable people out there and IMO thats not really fair.