Why people want to beat up nerds?

I never quite understood where this despising of the nerd came from. I know there dudes that are athletic and develop muscle mass quite easily (good genes) and there are dudes that can absord massive amounts of data in a short laps of time (good genes). If they both possess good genes that permit them to get ahead. Why do nerd get to be so unpopular?
Why people want to beat up nerds?
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