Why are facts perceived as arrogant?

If I were to tell someone that the Democrats started the Ku Klux Klan, then provide proof of this, but the other individual rejects the proof and claims that Republicans started it (with no proof of their claims). You then decide to call them a dumbass (because they are), and acknowledge your rightness to their face. Please tell me how this is arrogant?

Why are facts perceived as arrogant?
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