Thought on how well one does in a game?

Okay so i have a buddy i consistently play with and he always rages when we lose and for this example ill give my last game played, So i was ahri mid and he was riven top and it was a tough match up but i started out bullying my lane opponet and i believe he did to but later into the game the adc etc began to get fed so. the game ends and i was 8-10-18 while he was 14/14/6 so he started raging sayin the team was worthless because we all went negative but yet his damage to champs dealt was 30k and mine was 35k also he says score is the only thing ithat matters so by that logic i deal 2k damage to champ and someone comes in and hit q and deals 100 damage? thats means they did more work than me? lul also the reason teams win for most part is a gold advantage/ he denies that as well says its soley on kills he also doesnt think assists matter at all but as i stated before i deal 2k dmg they deal 100? that assist didn't matter? What are your thoughts do you agree with him or me tell me below.