They didn't just choose those criteria out of thin air. They compiled data and ran a logistic regression that was able to predict whether or a not a given user would be banned from a web community based on the content of their posts. And it turned out that negative words, profanity, spelling and grammar were all predictive features in determining that result.

Here's how science works: If you don't like the conclusions, you can question the methodology. You can conduct the experiment yourself to see if you can reproduce the results. You can run your own studies and see if you come up with different conclusions. But you don't get to say "Hmm, the data don't conform to my preconceived notions about how the world should work, so I reject their implications."

Everyone doesn't agree with the idea that every thought from every person should be heard at all times. Some people are just jerks. "Trolling", by definition, is about making provocative statements to incite reactions, as opposed to contributing to conversations. There are places where that kind of thing is accepted (4chan) and places where it is not (hn). Tools that help communities to encourage their preferred forms of communication are good things, and will be increasingly important in the future.