I think there is another dimension to this. If a player is releasing steam due to tilt, I think it is useful to know that. Poker-related information is always useful.
I can understand the sentiment of the OP. However, while the maxim of only saying good things about people is noble and would make the earth a better place, it is unachievable even in real life, let alone on the Internet.
I have never turned off an individual chat because I feel that additional information is useful. An exception would be if they are chatting about something completely unrelated to the game. I have had only one extreme case where a person kept saying the most vulgar sex-related things. I warned him that if he continues, I will contact support and his chat will be suspended. He continued, I emailed support, and his chat was suspended.
I sometimes flame people for idiotic plays. Strictly speaking, I shouldn't be doing it because it is a waste of my time. I usually do it at freerolls
if I am not multi-tabling. I generally use words that one can hear even on PAD. Interestingly enough, this results in many players assuming that I am on tilt and this benefits me since I usually play tight against such opponents and getting called more is a net benefit for me. I just want to point out that I am not flaming for that reason, as say Tony G does.
In summary, I think it should be recognized that this is the Internet and that the standards of communication are lower. While this deosn't mean that anything goes, we cannot expect to have the same standards as live communication. In addition, at poker rooms, people meet each other for the first time and often for the last time. This encourages even looser language.
But from the point of view of poker, any information about a player is helpful to me. This is why I never turn chat off.