Why are some people so rude and sarcastic when someone asks a question?

I see people asking genuine questions about problems that they have (has happened many times to me too) , and while some answers are really meaningful and help a lot, other people just seem to resort to name calling and being downright nasty and sarcastic. Why do you think this is? Are these sort of people living in perpetual anger? Or have low self esteem issues and seek to be "noticed" by their horrible answers, since they're not noticed in any other way?