I can believe this because the footage in the BBC film isn't anywhere near the worst I've seen of puppy farms. As puppy farms go the one shown was "good".
Often the dogs are kept in much smaller cages with wire bottoms, the cages are stacked on top of each other so the dogs waste passes through the wire onto the dogs in the cages below. The waste is not cleaned up and when the dire situation comes to light and rescue organisations go in they have to wear respirators and eye protection because the air is so thick with ammonia it's harmful to health. Many of the breeding bitches kept in those conditions have impaired sight because of the corneal ulceration caused by ammonia fumes.
Matted fur may grow around limbs so tightly the limb dies and literally falls off, other dogs have to be cut out of cages because their fur has grown through the wire.
The breeding practices of puppy farmers mean that dogs with health conditions are not screened out of the breeding program so puppies from puppy farms are more likely to have chronic health conditions such as epilepsy, kidney failure, hip dysplasia and dental problems.
Dogs from puppy farms will be removed from their mother and litter mates far to early and the lack of human interaction means they will not be well socialized which increases the risk of behavioural problems. Choosing a puppy over a rescue dog is not the way to avoid a dog with behavioural problems.
I do not approve of many farming practices and I do not eat meat but I have had quite a bit of exposure to sheep and dairy farms and have never seen conditions for animals as bad as they are at your a stage puppy farm. Regulations and necessity mean that you cannot breed livestock for food without some veterinary intervention and a vet would be obliged to report a farmer not adhering to the standards for animal welfare.
Comparing raising animals for food to puppy farms proves the point I made earlier in the thread about adults being unable to distinguish between want and need.
If you don't eat you die, if you don't have a dog nothing bad happens to you.