Some good points raised...
Some pet shops & staff are excellent, and some breeders are downright frightening. However, the odds are that breeders are more knowledgeable and better able to provide proper care advice. That won't change unless pet shops start paying people enough that they could actually consider it a career move to work there, which is unlikely to happen.
Pet shops sell animals that are WC or of unknown origin in many cases. Most breeders don't.
To answer the original question, I think it is worse for a pet shop to sell something they don't know about, since they SHOULD know better, than it is for a beginner to buy something there- the word beginner says it all, and so they could be excused. Not sure what the point of such a comparision would be, though.
Hopefully, breeders don't sell non-feeding animals and 'runts' to pet shops. We sell most of our offspring to pet shops, and they are all well started (4 feedings, minimum) before they go out the door. I would never sell something that was not feeding or was a 'runt' except in exceptional circumstances to someone who I was quite confident about and with complete disclosure!