Theres no doubt IMO that it started off as a legitimate concern. As I read through it, I agreed and was just dumbstruck by how they could do that etc. But then as the thread went on, I found it quite easy to see that it turned into a joke as it went along. Quite often not everyone follows it, especially over a text only medium, in a situation where body language and tone has a lot to do with it.

eg: A serious discussion about politics can degenerate into a friendly insult contest and comparing each other to horrible things, which makes for a great laugh when you take into account the tone and body language, but take those away and it turns into a flame war.