My wife and I have two male GSDs one is almost 3 and the other is almost 1. Both of them have been heavily socialized and are very good with people with one exception... The older one has ZERO tolerance for anyone who flinches or acts scared. If you ignore him and/or act confidently around him there is no issue, but flinch or take a the long way around him and he will get very agitated very quickly. Any advice on why or some tips to help?