Why do people think it's wrong to breakup with someone because of someone else?

when your in a relationship you don't close doors to other people by not talking to them. your not married! If you found someone better and I don't mean this in a shallow way I mean considering personality and physical attraction. how is that bad?!? if you thik about it people breakup with other people because of arguments right? that may be the main reason but I think people think to themselves ';if i see if i could with someone else who's better (not just looks but the whole package) then i would dump by partner and stop putting up with their crap';Why do people think it's wrong to breakup with someone because of someone else?
you are a cheater and your gf deserves a real man. A girl that goes with a guy that has a gf gets used goods! Are you being honest or playing 2 women?

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