Just Why?

Recently I've been playing a lot more League and I've noticed that the more i play the more common it is for players, my teammates and the enemy, having a really awful mindset " I'm playing X champ in X role and if you don't want me to or pick something I don't like I'm feeding." That said I've played long enough to have a pretty thick skin when it comes to things like this but in this case (check link for Vod) it just really annoyed me. Normally I just report after the game and leave it at that be I don't know I feel like this is growing into the predominant mindset for players and not just in my Elo but over all. Now the vod I've provided is from a All-For-One game where it was decided we would play Rumble and right from champion select the player stated if we played Rumble they would feed. Seconds into the game they gave up first blood and kept giving kills until the enemy have a very heavy lead on us and began roaming and picking up kills and those of us who were trying to lane. I realise we could have easily not died had we turtled in tower and farmed but put frankly I'm really bad at this game so the enemy had an easy steamroll and it wasn't until we proved that we could actually fight together and win that they began to put some form of effort into play but it was too late and we ended up on tilt and surrendered shortly after. What pisses me off the most is that not only did they ruin a game that had the potential to be a really good brawl but they showed a complete lack of concern for the consciences of their actions. The whole "Sure go ahead and report me Riot isn't going to do anything to me i'll just keep trolling." I know this is more of a rant but I just don't get why people do this to other people and how they are allowed to just keep doing it to the point that have no fear of being Suspended or Banned. Anyway I've said what I wanted to so yeah please look into this and take action, I don't care if you suspend them or whatever just try to promote the Environment that Riot always talks about trying to promote.

P.S. Any suggestions for how to try to get a teammate back on track or keep the rest of the players from tilting in a situation like this?