I think patriotic pride is a product of indoctrination. When you see someone become very reactive over a belief it's because it's deeply ingrained and there is a strong emotional bond attached to it. People get indoctrinated very young. Children have no idea or choice and follow through as adults unless it's fractured at some point and they start thinking for themselves. (Of course, they grow up in an environment rich in propaganda that nurtures and reinforces their invisible belief system. Which is why it's so hard to reach some.)