Stephen Fry gives a fairly standard atheist answer to the question, “What would you do if you died and found yourself in front of God?” — exceptionally well-stated, of course, but unsurprising. The best part is to watch the expression on the face of the interviewer in the various reaction shots.
Another factor, to me, is that if their afterlife were true, they expect us to stand before a deity as a supplicant, with a vast power differential, and then essentially grovel. There is no human dignity and no hope in their vision of death — your choice is to submit or suffer. If this god could see into our minds what we were truly thinking, then there is also no point to pretending, and it would know it: this would be a monstrous alien passing judgment on a humanity it regards as corrupt, debased, and wicked, and the only propitiation it could get from us is our terror.
Fortunately, there is no evidence and no reason to think we will continue to exist beyond the death of our bodies, or that there is such a cosmic tyrant, so I’m relieved that I don’t have to worry about a Christian afterlife.