Seriously, ever get teammates who you swear would try and gut one another if they were brought face to face? Happens in about 50% of my games. I just try to ignore it as much as possible, but sometimes it gets out of hand.
It only seems like this because of anonymity. Without having to put their physical selves behind their own words, these people don't have a 'filter'. Put the majoirty of them in any sort of IRL situation and see the results...
Creating a game that people love as the favorite past-time while giving so many people anonymity and then telling them all to work together to achieve a goal stresses a lot of people out and flaming is the go-to stress-reliever for them.
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Really though, I think all of that behavior boils down to, "this is violent, and unnecessarily so." Solving that kind of talk requires approaching it with rationale, and in some instances it sounds like mute is the best way to go.
That being said, serious threats should never be taken lightly and you should inform Riot of that kind of behavior as soon as possible.
if they met irl they'd probably just jump on each other and melt into one of these: http://cdn.bulbagarden.net/upload/thumb/7/7c/089Muk.png/250px-089Muk.png
