The problem with universal atonement is that it doesn't pay for anyone's sins, or all would be saved. It only makes works salvation possible for those who save themselves through obedience.
Accepting a gift is not obedience nor is it a "works" Dave. It is generally seen as being impolite to NOT accept a gift from someone.
Just because the sins of the world have been paid for does not mean that all will accept this free gift from God. Let's say a friend calls and say's they just ordered themselves a pizza and decided to be generous and purchase one for you to simply pick up in your friends name. If you decide to not pick up the pizza for whatever reason, that pizza has still been paid for, yes?
Sry, I know this post is pretty old but, I just happened upon it. :)