Alright. I've skimmed the whole thing.
As the resident professional in the area of canine caretaking, I've some points to make.
1.) All dogs are capable of being aggressive. Some breeds are more prone to developing aggressive behavior due to the origins of their breed purposes. Guardians and Terriors breeds are in this catagroy due to the purpose driven nature of their breeding. Other breeds often include a sharper temperament due to being high strung, high energy or just flat out bad breeding. Breeds like border collie, pointers, setters, other herding breeds, and Siberian huskies can be snappy or snippy simply because their energy wasn't directed into more positive avenues.
Toys are often problematic as well, due to poor owners and really rotten breeding practices. Any breed that has been a "fad" breed is victim to bad genetics perpetuated by jerks out to make a buck. Chows, white German Shepherds and Dalamations (thanks a lot, Disney!) are some examples.
Inbreeding and bad breeding can result in flat out crazy. Never trust an Aussie with a lot of white (and just keep distance from the merles) the flashy coats are popular, and unfortunately, resesive.
There are breeds that I do not trust an inch unless I know the dog and how it was raised. Akitas, Chows and BRTs are the front runners. Pit bulls don't even rate a "meh" on my scale of difficult breeds. Which is not to say I haven't met (and handled!) Pits that made me want to poo poo in my pants, but when a new pit walks in the door, I don't have an "oh, *expletive deleted*it!" moment, like I do with Chows.
The owners really do make the difference, and the smart ones know what their dogs are capable of being, how to interact with their breed of choice and know how to handle it. The idiots with ANY BREED are the ones that make my life hell.
(Oh, Airdales. Add Airdales to my list. Now that's a tough breed)
2.) Fighting pits are raised bad. They are bred from the dogs that have survived fighting, with no regards to genetic lineage. The are not handled beyond a bare minimum (if that) they are caged unless fighting, often they are starved, abused or tortured in an effort to 'make them mean'. The rejects are killed or abandoned. One of the sweetest pits I ever met was tossed for being too sweet. Her only fault was she was hugely kennel aggressive. Without a fence between her an another dog, she was a submissive puddle of love.
Others are not so lucky. They are not safe. They should be destroyed. It's not their fault. You'd be mean as a snake and twice as dangerous, too, if you were raised like that.
Pits raised be good owners are generally good dogs. Pits raised by well meaning idiots are often sweet, but have little to no manners. Many pits are naturally dog aggressive, which, IMHO, is not truly a fault, as long as the owner is aware and makes a point to keep the dog under control.
3.) Someone brought up Dachshunds? Yeah, no, the modern ones (even the toys) still have plenty of that old instinct. They can be pretty snappy. Just FYI, don't walk up to a strange one and stick your hand in it's face. You may not get your hand back.
