This is one of the better articles I've read in a long while. There is an old adage that we shouldn't discuss politics or religion if we want to get along with others. But social media has added infinite other topics to the list.
In a great way, social media has bred a culture of argumentation, nastiness, disrespect, and impatience. Now that we have the biggest exchange of information in history we tend to abuse it and take it for granted. It's always open hunting season, and everyone is a hunter loaded with ammo in the form of harsh words, ad hominems and other logical fallacies, and just plain contrarianism.
You mentioned that there's a missing model for online etiquette (not your words). So true. And you wrote a number of typical responses of disagreement, but the one that may be most egregious is one that contains a complete lack of any substance, value, or intelligence, such as a response that states, "You're an idiot." And there are also too many responses that make suppositions about a poster's experience and background.
It's pretty obvious that the bad must come with the good, and I am waiting to see if we collectively reach a tipping point where people get tired of all the derision and divisiveness so that we can really speak to the issues at hand.