Spider genetic "defects" have ZERO impact on their health and longevity. Taking your dog example, brachiocephalic dogs have insane health issues relating to a genetic breeding program that produced these dogs so that they only "look nice". Same with hairless dogs, giant sized dogs, and long haired dogs.

I will put my spider up against any ball python for feeding, temperament, health, and longevity. Nobody should bash something they know nothing about simply because they read or saw it somewhere that uneducated people assume it is a defect and state as fact. I bought my snake because it was beautiful, calm, and a price I could afford. I would happily take a normal over a morph any day, I just happen to own a spider which has taught just how wonderful and amazing this morph truly is.

By your logic breeding any animal is careless because breeding in itself produces unwanted genetics that evolution naturally would have weeded out. Ignorance of something is no excuse to pass judgement.