Why are people so narrow minded?

So recently I've been leveling another account and my goodness the level of toxicity is incredible. For instance just now I curbed a Darius in lane, he was obviously a new player so I stopped killing him after 3 deaths. Then after his 4th death the enemy Ezreal and Katarina would constantly talk shit about him in all chat and no doubt did much more in team chat. Sadly this happens insanely often. I have about 20-25 normal games on that account and a majority of those games has had atleast one toxic person usually flaming someone who's feeding. Keep in mind this is level 15 and below matches and the fact that many new players are being bashed is actually pretty sad.