Out of a couple million players, Im fairly sure Riot isn't choosing to single you out in particular. I also am guessing that it isn't every time and you are overblowing the actual issue. Not a bug either.
There are things you can do to help combat this problem. One is simply: play bottom yourself and take up one of those spots. The other options are simply to win your lane and roam to help them win theirs more easily or focus the fed bottom lane in teamfights. Learn how you can improve and help your team instead of how they can improve and work with you.
If people are flaming you just mute them. I had a premade 3 in my last game that were using racist slurs/random spamming so I just did a /mute all. We won the game and I was still able to communicate through pings with them.
Just keep your head up and move on. Report as necessary if they are deliberately toxic, NOT having a bad game.