Don't worry your not alone, because I feel the same way. Like everyone said, Ignore them if they start to insult you or if they gone too far mute them in chat straight away and don't hesitate to report them after the game.
The LoL community sucks in general, you'll often meet people who are complete jerks who thinks they have more skill than others but sometimes you'll meet people who'll be friendly and nice even if you make mistakes. Look don't let these people discourage you from playing the game and enjoy playing, it's just a game after all.
As for me, I'm really friendly towards my fellow teammates even if they make really bad mistakes. You can add me if you want and we can play a game or two