League of Legends (LoL) Question: how to calm people down?

Personally I just mute people like that. If you ignore them and just play your best every game, sometimes people just stop typing and get back in the game. It's also the best way to make sure their attitude doesn't negatively affect yours.

One of my friends is good at talking people down, but if that kind of thing doesn't come naturally to you, it's safer to just mute.

That type of person doesn't go away no matter how high you get and the best solution there is for it is to mute them. Typing to them makes you unfocused and not playing the game to your full potential because you start to get worried/concerned about them raging.

https://www.youtube.com/watch?v=-w2HWoiXlqM

Start at 3:30 on the video and I would recommend going through his series. It's quite good.
Valkrin is the new TSM substitute as of a couple weeks ago.

Don't forget they also went to play the game for fun and glory. Once I see people start flaming I usually just type "Relax". Just that, nothing more. It works more often than not and it doesn't cost you a lot of time. Repeat it if you have to later. Just avoid a discussion at all cost, it takes you too much time and you might lose your focus or start tilting.

Whatever you do, don't get caught up in arguments. Even if you're absolutely sure you can verbally one-shot them it's still a gamble how they will react. If it's unavoidable, keep your goal in mind: winning the game and having fun. Not showing people how stupid they are.

Sometimes you have to say a bit more to stop the tilt from spreading to other team members. It's pretty much too late by then anyway though.

I don't like muting because you lose sight of your teammates' mental states or you may miss some interesting information. If you can't control yourself (you absolutely have to react to every message) I guess it's an option though.

I also got placed in B4 this season after finishing last season in Silver. I know your pain. I realize that it's tough being called out for something that is not your fault. Honestly, a simple fix would be to turn off all chat and to mute any players on your team that are being negative. While you will rely only on pings for communication, its much better than being exposed to constant harassment. Some people are just determined to be salty and blame everything on their teamates. Thats true Bronze. Just making sure you're having a good time, and try to be the bigger person :)