Problem is, you aren’t dealing with the normal homeowner - you are dealing with someone who is losing their house, has no place to go, no money, feels scared and resentful, and has been hounded by many others like yourself.
If you are just farming a neighborhood, that’s one thing - but if you are knocking on pre-forclosure houses - you’ll probably mert up with something much more menacing than a cute little dobe.
BTW - I own a doberman and they are sweet as can be. :0)