Why do people get so toxic over a video game?

In one game (I was support because I genuinely enjoy playing support) three of my teammates deemed it necessary to use highly offensive language because of things either completely innocuous, or outside of my control completely. The Jinx I was playing bottom lane with repeatedly called me Re***ded for using Lux support (she was on rotation so I tried her), and every time i made a slight mistake started going on about how I was doing badly and was throwing the game, even though for the majority of the game I was playing at an acceptable level (hitting two out of three queues or so whilst zoning the enemy so they could farm). The Negative Negative Master Yi who flamed me for recalling to buy items before he died, don't get me wrong if he engaged then I recalled I would not complain, but when he engaged I was already at nexus and had already started heading into lane. The Garen who after i called the jinx out decided to repeatedly use the N-word, and later in the game said I can't report him because he was doing well. What I want to know is why people get so salty about normals, the place to learn and get better at champions and roles, I get that people inting in normals is incredibly annoying and makes the game unfun, but when people do badly they should be told how to get better and not told to uninstall the game or things of similar nature. The game i use as a point is from another account
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