On the other hand you go to get your computer fixed. The IT person tells you that your computer is slow and cant do anything because you have 39 viruses and some untold amounts of spyware on your computer. He suggests that you should backup all your documents and let him wipe the system clean. You disagree with him and tell him to install more ram to fix your computer because of an article you read in the paper. He installs it begrugingly and you return a week later having the same problems and stating that the ram is bad and he needs to replace it. rinse and repeat.
The reason IT people are nasty at times is because everyone believes they are an expert when it comes to computers. It is somewhat insulting that everyday someone will tell you to do something that you explicitly told them was a bad idea.