Decisions decide games, not mistakes
People think that what decides a victory and a loss are mistakes made, but that isn't always so. Sure, consistent mistakes in big team fights will lead to losses, but that isn't what riles people up and gets them upset, it's decisions.
When you decide that farming top was more important than TPing to dragon that lead to a loss of first drag, that wasnt a mistake, it was a decision. When you don't buy zhonyas as an ap mid against zed and he gets fed, it isnt a mistake, it is a decision. When you don't gank for a hypercarry to help them snowball to victory, that isnt a mistake , it is a decision.
Decisions decide games, and bad decisions can make others upset, especially if they inform you of the right decision. Stop acting like people flog you for minor mechanical errors when in reality people are getting upset when you knowingly make a bad decision and refuse to recognize it.