I was at my friends house once when we had such a person call, he was a very nice you man, extremely polite and explained that he was an ex-criminal, even told us when we asked what he had done, showed us his badge etc, and guess what I bought some plasters and a CD cleaner from him, I felt good about it that I was helping a young person to re-build his life.
I haven't had a door to door salesman for years or seen any around, (mind you I doubt that they would make the effort to come up a country road where I now live :-D) I remember once upon a time they were a nuscience, which is why I guess I did not mind this particular young man.
I'm all for helping petty criminals to make a fresh start, but as long as only petty criminals are on this such scheme, I certainly would not wish to help a s*x offender or pardoned serial killer, or even someone who was once mentally insane,

I hope that community safety is always put first. But a petty thief I'm happy to give a fresh start too.