
This is the same as having your baby daughter have a hysterectomy. She would not go through puberty so physically wouldn't mature as she should. Some people don't mind this.
Myself I prefer that my bitches arte fully groen and mature before cutting bits out of them that nature decreed have a vital role to play. Some people seem to think that it will have no negative effect. We all know how vital hormones are to the correct functioning of the body when they don't function properly. Any woman who takes HRT or has suffered from PMT will tell you how it can effect your general welllbeing.
For this reason alone I think it is totally unethical to neuter baby puppies. You are taking away a large chunk of their hormonal system which not only regulate their sexual characteristics and behaviour but also influence growth etc.
I have my bitches spayed at around 7 years as I choose to breed from them, but otherwise I would spay a bitch 3 months after her first season, or if she was still under a year old at the time wait until ater her second.