I can understand when people can't believe in some element or another of the Christian gospel. I hate it, however, when they reject the gospel because they've picked up a bad copy, and there are a lot of caricatures of the gospel out there.
One version I've seen looks something like this:
Why does Jesus have to pester you "worship me, worship me?" It's great how you saved us and all, thanks, but go away now.
After you get past the "oh my gosh I can't believe you actually said that" response, how would you reply to that?
The problem seems to be that this person sees Christian evangelism as Jesus saying "Worship me" as thanks for his past act of saving us. So the person making this error has picked up on the "Jesus died to save us from our sins" part of the message but is missing that you have to make a conscious decision to respond to that act.
My response would be to point out the part that is missing:
It's like someone saying that, because antibiotics were discovered, we no longer have to worry about that infection you've got. No! You still have to take the drug.
Yes, Jesus essentially "created" salvation. You still have to take him up on it.
This may have its root in how we talk about "believing" in Jesus. "Believe that Jesus died for your sins." OK, I do, great, see ya. There's so much more to it than we so often let on. More about that next time.