I was taught that one should never trust any animal. It took me a while to realise humans were included in the advice.Yeah, I don't really know about dogs *says the woman who used a dalmation to herd children*. I notice more Americans than anyone else seems to use them as guards, even for chickens, but given the prey drive I'm not sure how that works out in reality. I'm not sure I'd ever really trust a dog.
The dogs here were trained by other dogs and this makes a world of difference. It all goes horribly wrong when people decide they are going to train animals.
There are exceptions but you won't find many compared to the number of 'dog trainers'.