Why are some people so against belief?

If you died today and nothing happened you would not know it right? Well what if something did? What would you do if you found that a higher power did exist? Really my point is this, what is the hurt in believing? If God does not exist, and everything goes black on your last gasping breath you won't know the difference. It isn't like you are going to be able to come back and say I told you so LOL. But what If there is a God and you had to face him? What would you say? Just curious, this is a question I have always wanted to ask. Please keep it clean and unoffensive to anyone, Christian or not. I really want some educated answers and respect towards each other in this question.