In other words, it's just the way people are. It affects all aspects of society including CS. If there's one black mark I'd give CS about this, it's that it tends to have a greater percentage of socially mal-adjusted people, and so tends to hang on to this sense of superiority more than other cultural blocks. Most regular people eventually figure out that it's not really important whether the football team is better than the basketball team, or whether you bought a Toyota or a Ford. But people in CS tend to defend and promote their preferred systems with almost religious fervor well into adulthood. This can be very off-putting to regular people thinking of getting into CS.
When they become adults, regular people often move on to zealous advocacy of their preferred political system, nationality, or religious denomination. This often descends into violence, sometimes over seemingly trivial differences between the two parties. Personally I find that very off-putting: give me Debian vs. Ubuntu any day.