Why do some people on question & answer sites ( like this one) have to be mean and disrespectful to others?

I have asked questions wanting real answers or opinions, but I always seem to get about 10% of my answers as mean replies, personal ults and name calling. I have noticed this on other peoples questions as well. I was looking for an online forum to dicuss things and get answers, not be called an idiot or stupid and not to be insulted because I made a typo. I am looking for views that differ from mine or maybe like mine to stimulate the mind. I am home bound and this my connect to the outside world, but some of the replies have I gotten want to close the world out. I never realized how many mean people there could be out there.