I'd like to comment on a statement:
"It’s not comfortable keeping dogs with high social aggression in urban settings… I prefer more manageable and balanced dogs, only then I care about their fighting qualities."

A dog without social aggression is useless for protection!
The author is talking about what I call "softies." A true protection dog must have a natural, healthy level of social aggression; otherwise, it’s not a protection dog, no matter how much you train it.

For real protection (not to be confused with sports), social aggression is a must. Without it, a dog can’t act on its own, and protection is exactly that—an independent act (though not out of control). If a dog lacks this, all training will fall apart when faced with new, unexpected factors that even a well-trained dog without a solid core—without social aggression—isn't ready for. It's social aggression, not just love for the owner or a sense of duty, that is the main trigger for real, non-sporting protection.