Why do men take rejection so seriously?

This is just out of curiosity - but why is it if a girl isn't interested, you come up and ask her out - she rejects you and you take it to the highest personal level there is? Thank you!
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I would just like to say thank you to everybody who said something I just wanted to know that cause I rejected a guy once but I did it in a nice way - I never acted like a bitch all I said was "I'm sorry I'm not interested but thank you for asking!"
Why do men take rejection so seriously?
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