Working GSDs are generally bred for IPO (schutzhund or protection work) which means, among other things, being willing to bite people with maiming force («some level of natural aggression and protective instinct»). (atyourservicedogtraining.com)
Conversely, Lin said that if the VMHvl is inhibited, it suppressed natural aggression between males. (aaas.org)
I just want someone that understands my nature and can not only deal with it — but understand my natural aggression is not a bad thing if I control it. (religion.blogs.cnn.com)