Quickscoping is one of the things that made COD so popular. I don't mind it because 90% of the people who do it can't hit you with their first shot anyways, and the ones that are good at it are normally spinning in circles (
) before they shoot so they are pretty easy to kill.
The #1 way to make sure that you never get quickscoped close range is to dropshot (go prone while shooting) because they always aim high.