It's our relationship with dogs as having a special status. The moment you criticise dog ownership the pro dog brigade are on you like a ton of bricks, "my dog is harmless he wouldn't harm a fly", well until he does.
Some dogs are bred and trained for aggression, some are not. Some people are likewise aggressive, so should we likewise bundle all people as aggressive, just because of the few? It's completely unfair to bundle all people, all dogs, all dog owners as one.
My own dog, will bark if anyone acts strangely around her, but attack, hurt or in any way injure anyone she would never, ever do. Last week I was waiting with her in a bus station sat down, minding my own business all quiet and peaceful. Along comes a mother and 6 year old-ish daughter, and sits next to me. The child began taunting the dog, the dog began barking, the mother did absolutely nothing to stop her daughter. It went on for several minutes of taunting, and barking. The dog eventually decided it was a game they were playing, and was keen to play, but by then the mother had decided the dog was vicious, and went off tutting to herself about vicious dogs. Had the child been told to stop her taunting, there would not have been a problem.
There is nothing wrong with the vast majority of dogs, or their owners - it's just the few who cause problems and hit the news. I most certainly agree, as a responsible owner, that it needs to be properly and effectively dealt with.