Why do people hate each other like this is something i have never understood since i was little?

like instead of fighting each other why can't we just put our hatred aside and start building and making cool things you know theres sooo o much beautiful things that people make from everywhere and i don't understand you know???? sometimes i feel like ariel from the little memaid how she couldn't imagine the world that makes such wonderful beautiful things can be soooo bad i don't know maybe i'm just being emotional again but i can't help it i never understood it then and i don't understand it now =( *sighs*