Now, let me preface this by saying I do not promote toxicity. There are ways to convey criticism without being toxic. For example: "I don't think you should build a ZZRot portal on Sivir." vs "What kind of idiot builds a ZZRot on Sivir?".
Now, going on with my post, players have a very bad habit of responding to even light criticism with extreme toxicity. Just because I'm trying to criticize you and give you advice does not mean I think you're a bad player. I don't think you're an idiot. Ignorance is much different than stupidity. Good players, and smart people, can still make mistakes, because we're humans.
However, people seem to jump immediately to being hostile upon being criticized. Here are some examples I've dealt with lately.
Story 1: Had a Twitch ADC. Everytime he would ult, he would flash TOWARDS the people he was ulting. Every time. After the third time I watched him flash into melee range of a Mordekaiser, I told him he doesn't have to flash towards the Mordekaiser. I said, specifically, "You don't have to flash towards people, especially when using your ult Twitch." He became hostile, immediately telling me "Oh, so now you're harassing me? What the hell is wrong with you?" He then proceeded to call me an "idiot" multiple times and claimed he never flashed into the enemy team. He threatened to report me for name calling, which I said was hypocritical, and I never called him any names. I asked him to state what name I called him, and he said (and I quote) "You implied it by telling me I didn't have to flash. Don't you know you don't have to call someone a name to call someone something?" That, to me, is logical gymnastics at it's finest.
Story 2: I was playing top lane Aatrox. I managed to get my lane in a perfect position to freeze it near my tower. I had a good wave built up, and was zoning the enemy Jarvan perfectly. I was about 20 CS ahead, when my jungler came top. Their jungler was also top, so nothing really happened. Their jungler left to clear more jungle or something, and my Shaco stayed top. He then proceeded to hard shove my lane. Boxes, smites, his E, he was using everything to push my lane as hard as he could and take as much CS as he could. He did this for 2 whole waves, shoving it all towards Jarvan and completely destroying my lane control. I was pretty upset about this. Anyone who plays top lane knows how hard that can mess up your lane, and could turn a winning lane into a losing one. I called him out, saying "You messed up my freeze by shoving it towards him. You really fucked up my lane dude." to which he became hostile, telling me "It doesn't matter, shut up. You suck anyways." I tried to enlighten him to why lane control was important, and how freezing works. He responding "I don't care, shut up. I wanted level 6." We ended up winning, because I dove the Jarvan at 6 and proceeded to dumpster him in lane, but if we were two players on even footing, I easily could've gotten counter-frozen and just been zoned out of the game by J4.
Story 3: I'm playing Aatrox again, this time in ARAM because I'm playing with some friends. Game is looking kinda dodgy, Sivir is heavily behind (she was 5/11) and I'm one of the only ones doing well (9/4). A 4v5 broke out because the enemy Rammus engaged on our Karma. I went in, diving for their backrow. I got two of them, and died. The rest of my team got rolled over. Sivir came much later, and got dove and died. I tried to give advice, saying "Hey guys, buy magic resist. They have no physical damage." and Sivir replied "Can't you fucking wait before you engage?" Being a bit cheeky, but also just stating a fact, I said "Waiting for a 5/11 Sivir wouldn't have much impact on the fight, and I counter engaged." She said, "Okay, enjoy the 4v5 then" and threatened to AFK because I had "attacked" her. I simply stated her score. After the game (which we won, she got off her ass after we won a 4v5 teamfight.) she proceeded to call me iron garbage, tell me to kill myself, and to uninstall the game because I'm garbage and will never be good. I outdamaged her, had more assists, more kills, less deaths, more gold, and was the main tank in every teamfight.
Moral of the story, take criticism with a grain of salt. If someone is trying to help you improve, they're not calling you bad. They're trying to teach you, so that you can learn from your mistakes. If you think everything is the game's fault, and won't take someone else's point of view in what you're doing wrong, you will never improve.