I wholeheartedly agree with the OP.
I bought Mocha from a backyard breeder. I was an idiot and I didn't do nearly enough research...I knew not to buy from a pet store and to see what environment the mom and puppies were in, but that's about it. She cost more than the adoption fees at our local Humane Society to begin with, and only got more expensive after we found health problem after health problem. After $1500 in vet bills, we had a beautiful puppy who survived and is the apple of my eye. Do I love her dearly? Of course. Will I ever, ever do anything but rescues dogs again? Never.
When we decided to get a second dog, we knew it had to be small, non-shedding (as much as a dog can be), and it HAD to be a rescue, no exceptions. It was a rescue dog or no dog. So we adopted Panna, a 2-year-old, purebred Maltese with papers who was in danger of euthanasia. She was scared, as I expected her to be, but she's a doll. We do think she was neglected in her past (not abused), but we wanted to help a dog who had a tough past...we've had plenty of fosters through our door who have had absolutely no problems and were just happy dogs who needed homes. She's now been with us for a year and a half and we couldn't love her more.
Next we rescued Cannelle. We weren't looking for a third dog, but a rescue we foster for called us and asked us to take her...how could we say no? She's been severely abused, attacked by large dogs, she lost an eye, and, well, if there was ever a dog that needed love, she's it. She's come so incredibly far and seeing her transformation has been unbelievable. She's our miracle

.
Working in rescue can be sad, but it's far more rewarding. In June, I had a Yorkie X foster that had to be put down due to heartworm that had progressed past the point of being treatable. On the other hand, nothing beats seeing my fosters go into loving forever homes, especially when I see them a couple of months later and they're so happy and healthy.
I have never, ever been bitten by a rescue. My two are wonderful, not to mention that the support I receive from rescue is unbelievable. I mean there's different types of dogs with different temperaments everywhere, but I know that I will never go back.
Really, I figure that I won't support backyard breeders or puppy mills and the screening process is comparable for rescues and reputable breeders (a lot of shelters, on the other hand, don't have any screening process at all). However, I just can't buy a dog when there are innocent dogs in shelters, just looking for forever homes. Not to mention that rescues are considerably less expensive (which quite a few people seem very happy with!).
Jodiodeeo, that definitely sounds suspicious. Were the 150 animals well cared for? Have you thought about reporting them to your local SPCA so they can investigate? It's incredibly irresponsible for anybody, but especially a rescue, to have an "oops litter". I'm sorry you had such a bad experience, I hope this won't affect your opinion of rescues. Please let me know if you need any help with anything.