I have a brother who is a cop; his personality, outlook on life and general opinion of humanity has been drastically altered over the years, and it is a direct result of the fact that he deals largely with...for lack of a better term...the scum of the earth. When your interactions with people are heavily weighted towards the kind of people he deals with, it's inevitable that your perception of people will be altered. He expects the worst of everybody because almost everybody he deals with is the worst.
There are some good people around; but good people generally don't come in contact with cops and so they don't have as much of an effect on the cops' view of people and life in general.
Similarly, when you have experience working for the Humane Society, you get a lot of exposure to the sort of people...breeders, owners, whoever...whose evil deeds and faults bring the HS into the picture when animals are involved. But, again, your opinions and perceptions are skewed towards the negative; the many, many people who own dogs and cats and treat them like beloved family members don't show up on your radar nearly as much as the POS-types who attract your attention.
What is the answer here? Just keep on keeping on, with large chain pet stores selling the puppies that originate in puppy mills? Or outlaw that, and suffer the kind of damage to the pet industry that you foresee? Laws...both good and bad...are all politically motivated; politicians don't pass new legislation because they give a crap about puppies, kids, the elderly, the environment or anything else; they pass laws that they hope will make them look good to their constituents in the short term so they get re-elected; long-term effects are impossible to accurately foretell and in truth aren't really a concern.
I'm not pointing a finger at anyone here and saying "You're wrong!"...but neither can I say to anyone that they are correct either. I just don't know; being closer to the problem makes some folks think their opinions are much more factually-based and therefore more valid and accurate...but I think that they are actually a bit more "snow-blind" to the problem than they realize.