Ragers and Flamers

Hey Guys! I just played in a Norms Game where I was playing support and flamed by my ADC and my Jungler. So our Gragas started out the game making 2 mistakes and going 0/2. However, instead of playing better, he blamed our mid Karma. He continued to flame and called this team a trash team and blahblahblah. He called me a noob, where I was going 1/7/3 as Lulu (just bought her am pretty noob) so i responded by saying "yes I am". This game didnt make me rage but i've been wondering why some people act so good in the forum and go full demon mode in games. So here How do you guys handle ragers?