If you can get past the hyperbole regarding the Nazis and Eugentics, if you can get past the obvious one sidedness of the entire series, I think they do make a valid point, but they drag breeders thru the mud by only showing a small section of breeder. If you want the "in a nutshell" version, you can skip to section 6.
 
I recommend however, to watch the whole thing. A lot of the working dog vs show dog conversation is illustrated here, but not in mastiffs.

Edit: I should add, it is more the "show circuit" and  some of those that breed for it that are underfire.

http://www.youtube.com/watch?v=-1LyjlX4Mp8

http://www.youtube.com/watch?v=kcUbCvS0ZEM

http://www.youtube.com/watch?v=SpR5su-PQ0g

http://www.youtube.com/watch?v=QDKwbWA5Tdg

http://www.youtube.com/watch?v=Szl30xomLXo

http://www.youtube.com/watch?v=nFJffepQY3Y