I have a rott and she is the gentlest dog ever ... she is very well behaved and LOVES people. She loves kids as well and has never tried to hurt anyone.
We keep our dogs in our yard or on a leash ... and I keep all my dogs in the house as folks have a fear of my rott. I can tell you ... she's the best of the bunch and minds the best as well.
I fear that folks would hurt my dog even though she is inside a fence. It's because folks fear the breed.
I've seen and had different breeds of dogs be biters ... you should fear all dogs unless you know them already or own them. You do not know what any animal will do if cornered or if they feel threatened.