I've had dogs most of my life too... and ran my own petstore/aquarists for 7 years.

I can find nothing positive to say about dogs that have been purposely bred to be aggressive, and thereby potentially dangerous to small children or babies... no matter how well-intentioned their owners (usually with less brain cells than their animals) may be, or how much they may sing their praises.

A dog just needs to make a lot of noise, if you're needing one to patrol your property.
You don't want to be worried about whether it will maim or kill the child of one of your visitors or passers-by.

Actually, Chinese Geese will probably do a better 'watchdog' job.

Have another look on youtube and read some of the comments.