The thing is, name calling the author provides no useful information (being nice and being mean can be equally useless if you discount interpersonal dynamics). It's just injecting noise into the post. And it's how the post opens so it does set the tone for the rest of the post, and people will be less inclined to read beyond it because the only signal provided in the first sentence suggests that the rest of the content is likely to be an emotionally inspired rant.