Healthy critism allows the other party to see the good and the bad, giving compliments about things that were good and negative comments about the things that are bad. That is not what is happening right now. Because of all the negativity, it becomes hard to enjoy the game itself, unless you block all chats. And that really shouldn't be needed for other players to enjoy the game.
Negative things stand out more while good things are sidelined. Because a good thing isn't an issue, it's agreed upon, it isn't as relevant. Negative things are hot buttons, things people will feel strongly over. And when people feel strongly about something it becomes hard for some people to speak in a civil manner. And, as previously stated, the language of the internet is vitriolic and hyperbolic because that is what garners a response. You can combat this by not doing that. Be reasonable and attentive, hear what they say and don't be afraid to agree that something could be better, because it usually can. Sometimes the aknowledgement that it can be better is all people want.
Of course, I am of the opinion that turning off the chat in most games is a better experience, or at least have the ability to tune it out. It's important to remember that most of it is just noise, people clamouring to be heard and their viewpoint validated.