the reason is that you are carrying a gun, how are they to know that it is legal for you to do so? just your word?
Should you have to go through a check-point every time you drive your car?
I would not intentionally carry in front of a cop just to provoke them, but I also do not feel like I should be hassled when I am doing something legal.
Where do you draw the line? The guy in the link has rights.
I would have shown my ID, but that is just me. (Yes, I do open carry. But usually it is around my property or when fishing.)