When teammates start criticizing each other, unless I think the game's already lost, I'll usually jump in with "Save it for after the game, guys". Doesn't always work, but it sometimes does - people realize on one level that their *****ing does hurt the team... and they do want to win, after all.

Leeeeeroy Jenkiinnsss!

Anyone that thinks that there is such a thing as THE build/strat for any champion is already a bad player, so you can safely ignore anything they say after that.

You always should adapt your build and strategies to the situation, be ready to get an extra small defensive item early if you need it for example, or use a totally different build based on team matchup. Item builds are NOT set in stone, and many champs can and should be adapting their ability builds to their specific lane matchups. If anyone is calling you a noob because they think your item picks or build choices are wrong, chances are they have no idea what they are talking about, because they are not playing your champ in that particular match.

In my experience, the person blaming, raging and belittling other people usually tends to be one of the team's worst players if not the worst, almost every time ending up with the most deaths even if what they are raging about is other people feeding. This is because they are concentrating more on other people's play (and typing about it) than on their own, and need someone else to blame for the inevitable losses this causes many teams they are in. Just pay them no mind, adapt to the situation, and keep concentrating on your play, safe in the knowledge that they really are just poor players looking to vent their frustration.

/mute is a good counter to idiots...
/ignore (after game, in game client doesn't do it for the server) to ensure you never see them again.

The more you filter, the more likely you'll find players who fit your mentality better, why do you think my $^#%^ing has lowered?

Not all games are May Sunshine and Pony Rides, I can tell you that...

LOL.. well, that isn't exactly what I was talking about, you are really just communicating and trying to be helpful, maybe sometimes getting a little frustrated. I've done that too, I meant more like actively trying to make players feel bad about themselves and calling them names or starting giant extended arguments or harangues in game chat about their play or their build.

The types of players that do this are the ones I am mainly talking about. In my experience, a lot of the time they tend to really just be trying to shift the blame from their own bad to mediocre play and almost always spend entirely too much time typing for their own good.

Pretty much, at least in the games I've been in, if I see somebody being a real jerk in chat: constantly attacking someone, arguing/saying stupid stuff, or obnoxiously calling someone a noob, that person is the worst on their team, almost without exception. A fact which I often gleefully remind them of at the end when the scoreboard proves it (hey, I'm a jerk too... I just like winning, and realize that yelling at my teammates during a game is usually not the best way to do that).