I agree that if he didn't know or didn't tell you that she was pregnant, he's an irresponsible breeder. We can all have "oops" litters, but it isn't that common.
By the way, we do encourage terms like "irresponsible breeder" or "unethical breeder" rather than "backyard breeder" here.
Many of us here at RT (myself included) breed and raise rabbits in our backyards, so "backyard breeder" is a bit misleading. It has been given a negative connotation that it shouldn't have.
This may seem to be nitpicking, but we recently had a couple of new members who went through this. One, being familiar with "backyard breeder" being a bad thing, used the term that way. The other came in worrying, "Oh no... I keep my rabbits in the backyard... is that bad? Do I need to move them? Maybe I can find room for some of them inside..."
So that's why we try to use phrases like "irresponsible breeder" instead.