I opened carried at walmart and nobody said anything to me...perhaps it's how you carry yourself while armed.
Your conduct and general appearance play a huge role. HUGE.
I have no hard evidence to support this, but I believe that most (and there will always be exceptions) situations where open carry results in a problem occur because the people doing it would otherwise cause people to be nervous or suspicious even if they were not visibly armed.
Logically, however, you'd think people would get a clue. How many criminals go around with a gun showing??? Hint: criminals and people with criminal intent hide their guns until they plan to use them.