why do players call other bad when they are in fact doing bad?

like last game i was paired up with another diamond player he had 70% win rate overall so decent player had couple golds and a plat 2 player. Everyone but me and the other diamond fed ,3-10 ect most damage at the end me and the diamond and these kids just shit talked all game long that we were playing bad which makes no sense because even if what we were doing was wrong (it wasnt) its still better then them so talking is just stupid yet so many players do it lmao.

I just dont the logic behind being 3-10 or doing extremely shitty and then saying someone doing 30x better than you and that is way higher elo than you is bad. If I was that guy I would just laugh my ass off like yes gold player feeding and crying in a normal game you tottaaaallly know it all lmfao.

tldr: where do ppl get off? 404 brain not found?