You have to take into account that non-English speaking people also play this game. And since being frustrated with your team mates happens, pinging is usually the only way these non-English speaking people will express their frustration. This is particularly true in the early AM or late PM.
Flaming is usually, similarly, someone that is just frustrated with their team mates. And, as I've posted recently, discourse between team mates is part of a healthy game. The issue is how its commonly responded to. Players should deescalate flaming and try to come to an understanding so everyone's time and effort isn't wasted.
Trolling, or intentionally giving the enemy team an advantage though game play or indirectly through chat with your team mates is deplorable.
Remember. It is just a game. But it is a competitive game. Everyone should be trying to win.