
The word 'probably' means that they have stated that the existence of God is unlikely - but nonetheless possible! Doesn't that resonate better with agnostics?)
Secondly, if as implied, Christians aren't enjoying life - then surely they are doing something wrong!
Thirdly, I suspect that they are equating 'sin' with 'enjoyment'. As the atheist has no concept of 'personal sin' and consequences - perhaps they may be forgiven for what is their simple ignorance.
Even so. Three blunders in eleven words is not particularly good going - is it?