That's because 99% of human decisions are made emotionally. We may be masters of justification, but ultimately the decision is made emotionally, using logic and rationale to justify our emotional needs. If you sway someones emotion, they will justify their emotional needs by whatever means at their disposal. This is why manipulation works.

This is also why religious debates and wars transpire - even in a developer environment where we pride logic and meritocracy above all: Visual Studio is clearly better than Eclipse, the PC will always be better than the Mac, Android is better than the iPhone and Git is better than TFS ;)