While I agree with some of the messages, I think they once again over simplify.
For the first ad against pure breeds. I have owned mutts and I agree they are great dogs, but...
Different breeds have different personality traits. When you cross breed you are not sure which traits you will get. If you cross a shepard with a springer spaniel, which traits will you get? Nipping or mouthing? Brains or dumb as a rock?
Also, if you know the dogs lineage you have a better idea of the health risks the dog will be prone to. By lineage, I don't mean breed, but rather, "did the parents have joint problems? If so, this dog will likely have joint problems as well." While you can get that with mutts, it less likely you will be able to check into the lineage.
I agree mutts are great dogs, but it is also good to know what you are getting.
For the second ad, I agree people should get their dogs frolm shelter, but give the thousands of dogs that have been killed under P.E.T.A.'s care, I have trouble seeing past their hypocritical stance.
The third ad, while I agree that breeders produce too many dogs and to off load onto shelters, I think trying to draw a parallel between human pregnancies and dogs giving birth kinds of like comparing apples and oranges.
As a side topic, I was talking to someone who saw a show on The Learning Channel or PBS or Animal planet on how dog breeds have changed over the year. One example was the British Bulldog, which 500 years ago was actually used for herding cattle and could single handedly bring down a bull. Now they have been bred down to a size where they could be a lapdog. I would like to see this show. If anyone else caught it and knows the name of it, please let me know.