I have just a couple of things to say.
Just becouse an animal is netured doesn't mean they don't have the pleasure, I have seen many of my male cats enjoy themselves on a pillow(as disjusting as it is, and I have always felt sorry for the poor pillow) But as for girl dogs, I am sure that is they knew, they would kinda be thankful. What woman wouln't like to get rid of that monthly vistor?
I cant consider fixing and animal as mutliation. If my parents had my tonsils removed at a young age(as some be do) to prevent illness later on, would they be mutilating me? Sure, there is nothing wrong with them at the time, but why take the risk? It isnt like you are cutting off a leg, the dog will relise something is wrong. Fluffy isn't going to lie awake at night listening to her biological clock and seeing dancing puppies.
Another thing is the sexist arugement, "boys don't have puppies, why should they be fixed" just like the teenage girls get the rap for having the babies. having and unfixed male, cause accidents can happen, you never know. Personality, I wouldn't want the responsiblity of knowing I could have been at fault for puppies dieing....
But...as bad as it sounds...and as hard as it is to explain, I think something would kinda be missed in a world of only the top 1% of dogs being breed. Everyone would have a breed. I love muts, they are so unique, I mean, my adult is 5 years old, 110 pound burly long haired dalimation like ball of fuzz, sheds like a blizzard, but has spots. wonderful dog, and I have never seen another one like her. We were told my puppy is st bernard boxer, but I don't know, I just know is adorable and the she is going to be big. I love her. I guess what I am getting as, sometimes, I i like the supize of a mutt litter. When I was younger, my mother worked for a vet, and they woul get pregenant animals brought is to be euthnized all the time....She would bring them home, we would raise the litter and the give them away to friends and family(and keep one or so~.^) It was always kinda exciting, cause you just never knew what would get....