Orcs and elves have had a history of conflict. They all say different reasons, but the popular consensus is as follows-  

Why Elves Hate Orcs

Elves made the excuse that they hate orcs because of their bloodthirsty tendencies. They say that their warring methods are sick and not thoughtful, and their lack of mercy makes them into lesser beings. They also hate their primitive traditions, and say that their lack of technology just shows how truly dumb they are.  

Why Orcs Hate Elves

Orcs have said that their reasoning behind hating the elves is because of their supposed superiority. They say that their tendency to believe that everyone else is below them gives them headaches. They also say they hate how posh and uptight elves are, stating that they are scared to “get their hands dirty.”