You've gotten some answers about what you should do and should not do; why some people are rude, etc. There is a culture to Usenet, and an etiquette, called netiquette. In the old days it was pretty easy to find out about what was accepted and what wasn't, and the old timers mostly learned it and follow it. Newcomers frequently run afoul of the conventions and are corrected, sometimes gently and sometimes not.
Take a look at the groups: news.announce.newusers and news.newusers.questions
They should give you some ideas of what is and is not acceptable on newsgroups. There are probably some FAQs on the web somewhere; a search on Usenet should uncover some info on netiquette.
You need a bit of thick skin here. If people are rude and obnoxious to you, chances are they are the same way with everyone else, and everyone else knows it, and before too long they have a reputation. The best response to them is to ignore them, or if you must reply, be polite. Generally they thrive on negativity; just don't feed it. They won't get any better or go away, but they'll be less obvious.
Don't respond to people in anger. Wait a few hours or days. After that time more than likely you'll see that their comment doesn't deserve any response. If you still need to respond after a while, you can generally craft a much more effective flame when you're thinking more clearly.
Welcome to Usenet. The people who are kind and helpful far outnumber those who aren't, but sometimes it takes a while to notice that.