My God there are some ignorant opinions being expressed as "fact" here. If the views like these weren't responsible for the deaths in pounds of thousands of harmless, friendly, healthy young dogs each year they'd be laughable. If we replaced the word "Rottweiler" with "Jamaican" all MN would be up in arms, citing prejudice, generalisation and gross stupidity, and rightly so.
Why do people own three dogs? People like me, you mean. Because we like them. Because they need homes - one of mine is a long term foster dog. Two of the three are... lock your children up... German Shepherds. Because most of us are responsible owners and our dogs are family pets and NOT dangerous. Nothing in Law or in the opinions of the experts - KC, rescue, responsible breeders - states that they are. Thanks for calling so many of my Rott owning friends and family thick and scum. 
Oh, and being ugly in your opinion does not make for a dangerous dog nor should it preclude responsible people from owning them. Apply that to humans and there would be justification in ridding society of an awful lot of our own species!
Additionally, that a dog attacks sheep (or for that matter is dog aggressive), as terrible as that is, is not indicative of a dog which is human aggressive. The two traits may be seen together, just as a man might be violent towards other men and women, but in the majority of dogs who are other animal aggressive this is not the case.
I know of gentle GSDs who live peacably with kids and cats (mine included) and snappy, stroppy Jack Russells. Some dogs are aggressive, there's no argument there. But they are so because of who they are, not what they are. If an act of aggression occurs, blame the deed, not the breed. After all, we don't castigate all men because some rape, or all Canadians because some drink-drive, do we?
So why am I angry when I'm not a Rott owner? Because, as I said, ignorance such as that which is seen here in the main proliferates fear and yet more ignorance and it costs lives. It causes dogs to be thrown into the streets, abandoned in pounds and sent to rescue, many of which, like the RSPCA, DO NOT have a no-kill policy and will PTS a healthy, friendly dog because no bugger will home him, thanks to mis-information on the breed and lack of genuine knowledge and experience.
As I said, I'm the owner of three dogs, two of whom would probably be feared and rated as dangerous by many of those on here.
I'm also a foster carer for dogs.
I'm a dog walker.
And I volunteer hands on for a no-kill rescue where I handle and interact with up to 80 of various breeds, including Rotts, SBTs and other bull breeds. In fact, one of their Rotts is a particular favourite, a dog which allowed me to manhandle him when he was paralysed by illness without so much as a growl.
More to the point, I'm an independent network rescuer. I have spent the past few years getting dogs into the safety of no kill rescue when they have been dumped into pounds, where without people like me they can be and so very often are killed either after seven days if they are strays or immediately if they are surrendered to the pound by the owner.
Healthy dogs. Young dogs. Friendly dogs. Innocent dogs. Some as young as eight weeks old.
I spend hours of my own time doing this, 365 days a year. Yes, I do mean on Christmas day too. I've sat up until 4 and 5am over the run up to Christmas, week in, week out, trying every rescue I know of to take just one dog out of hundreds, two would be a miracle, from pounds across the country.
I've cried rivers of tears, I still now never fail to be amazed at the depths of human cruelty and depravity towards these dogs... nor at human ignorance. There have been times when I have just wanted to answer threads like this with a string of expletives.
But I won't, because I won't let myself or those dogs down, nor will I sully the reputation of rescue. I won't ever give anyone the chance to say, "See? I told you so! Thick scum!".
Instead I'll write a long post, fuming as I do so, to ask you to look at the Deed Not Breed website and see how flawed the Dangerous Dogs Act is and how evil it is. You don't believe me and you think that if a dog is impounded it must be fair and just? Google "Save Lennox".
But moreover, I'm going to be bloody arrogant here and say something I've itched to say many times when this subject comes up and have so far just about resisted.
Walk a mile in my shoes. Go do what I do. Read a bit about my experience on Pets, where I have helped with advice and far more practically on and off the forum. Go and work with these dogs that you consider "dangerous" just because of their breed or looks. Handle them as I do. Sure, you'll meet bad ones. And many of those bad ones are the result of bad training or cruelty. Sometimes both. You'll meet the other side too, the huge, huge majority which are just dogs who have done nothing wrong, except perhaps be a Rottie, a Staffie or an AmBull and be waiting at the gate of rescue, hoping that one day someone will see beyond the headlines and beyond their looks and offer them a home. These are the dogs which never make the headlines, there are thousands of them in rescue across the country right now. You only hear of the rare, terrible stories as "Dog wags tail and plays with 5 year old" doesn't sell newspapers.
I don't profess to be an expert. I don't profess to be the best or the only rescuer on MN. But I do say this:
Come back to me when you have my experience of dogs, when you have walked that mile in my shoes and then put up an argument against any dog because of his breed or looks alone.
Because at the time of typing this I don't think any of those who have expressed the damaging opinions on here are arguing their cases on anything other than just that... opinion.