Why do people train dogs to be overly-viscious?

I love dogs. I always make friends with them at the home inspection, unless the dog is not into it, or is over-protective. I squat down low, talk in a gentle voice, and let them sniff my hand. Once they smell a stranger, they can decide if they want to be pet or not, and I don't push it. Most times, I make a friend.

Today, I was in a house in Amityville, NY and there were two Rotweillers in cages in the yard. These dogs were dying to get a piece of me. The owner stated they only will be friendly towards family members. I asked which junkyard they spent their days in and was given a look that said "what do you mean, these are our family dogs".

The neighbor spoke to me as I left, and she hated these dogs. One reason - she has children and she fears for their safety. She told me they trained these dogs to be that way.

I understand the need to protect what is yours, but this is extreme. Suppose one escapes. What if a fireman is attempting to save a life or put out a fire?

Maybe its me, but I think this is well beyond the normal realm of thought for dog obedience. This is like training a killer to kill.

-Ray