Because sometimes people are jerks?
NOTE: I'm aware of the inherent irony in pointing out that sometimes people are a bit thoughtless through the use of name-calling. That makes it double-irony!
More productively, sometimes it's a little too easy to get annoyed at a stranger on the internet and click that close button a little too quickly. We did just have the meta question that's germane to this point:
http://meta.mechanics.stackexchange.com/questions/1626/why-are-we-so-mean-to-new-usersWhy are we so mean to new users?
Just a reminder of the consensus: take a breath and think before reacting. You have time to avoid being a little abrupt and coming across as really nasty to our users. Civility, it's not a high bar.