Kim is right about the incontinence, some breeds have a higher incidence of it than others, and Dobermans are one of them. I have Italian Greyhounds, I have had four in total, all females. All were spayed at some point in time, and none became incontinent. On the IG email lists, spay incontinence is almost never discussed, because that breed is not prone to it.
Personally, I am more willing to take the risk of a Doberman bitch suffering fromo spay incontinence(which can be successfully treated in most cases) than I am to have her run the risk of mammary cancer, which is higher if she is not spayed. Spaying also completely removes the risk of uterine or ovarian cancer and the infection of the uterus known as pyometra.
I have to echo what Kim said about that website. Just because someting is written on a website doesn't make it true. I didn't see any scientific or medical references or justifications given for the opinions stated there. Also some of the things they said on that page simply weren't true, such as that false pregnancies are rare in dogs, they are in fact, quite common in dogs, and that neutered animals have trouble breathing because their chests are so narrow! That's hogwash. Think about oxen; what do you think they are? They are neutered male cattle. Yet they have broad chests and manage to do a full days' work. Most male racehorses are neutered, yet manage to compete in a demanding athletic sport.
I have spayed or neutered most of my pets at various ages. I have never yet had even one of them, whether dog or cat, male or female, become overweight as a result. My male Doberman is now 12 years old, he was neutered when he was 9 because he was having surgery for something else, he was never going to be bred, and he was hyper so I hoped maybe it would calm him down in some areas. The surgery he was having was for the removal of malignant melanomas, by the way, so he contracted cancer while intact, not that I think being intact or neutered has anything to do with it. The only change I have seen in him since he was neutered is that he has stopped humping the female IGs and the male cat. While I hoped for more positive changes, just that one was nice. He does not mark in the house, he has not become aggressive.
That website linked to appears to be a British site, they have a different mindset in the UK about spay/neuter, they are less likely to do it already than we here in the US are. Their stated goal is to make spaying/neutering completely illegal unless it is required to save the life of an animal. Given the ignorance of many pet owners I think we all know that would lead to even more surplus dogs and cats being born than we have now, and we have way too many now.
They offer the alternative of vasectomies and tubal ligation. The problem with those is that for the males a vasectomy won't reduce testosterone, so if there is an aggression problem there is no change it will help. If there is no aggression problem, then it's a moot point. But a vasectomy is more involved to do, I think, than a neuter.
A tubal ligation would stop a bitch from becoming pregnant, but wouldn't be of any help at all in the health area, as she would still be at risk from the same diseases as a fertile bitch.
I've lived with in-season bitches before, and I don't like it. If an animal is not a breeding animal I don't see any reason to require the owner or the pet to live thru seasons for the animal's whole life. It's messy for the owner, it restricts the animal's lifetstyle for about six weeks of every year. If you're showing a bitch in obedience you can't show her when she's in season, if you have unneutered males, and this site wants to require that both your males and your females be intact, you'll have to keep them separated while the bitch is in season. I've done that too, and it's extremely nerve wracking. Why do it if you're not going to breed the pet?
I haven't read the entire site yet, but I did glance at some other pages. They also have a page opposing tail docking. They didn't mention ear cropping, but that is probably because they are in the UK, where it is already illegal.
