Being demoted for someone going AFK

I can't be the only one this happens to; my team invades gets our adc 2 kills early, great start, our top side proceeds to feed 6 kills and then quits the game and at this point its too late to remake so we have to deal with it, then our adc decides to feed 8 kills and afk run it down, making the game a 3v5, and as a result i get demoted from this, when these games happen the players actually trying shouldnt be punished for the rage/anger/mentality of another player; I have been demoted because of this too many times idk if i have the worst luck with champ select or what, but 10 matches in a row is just too much.