Warren got stuck in the earthlies?
Huh? Where else are you going to find common ground when
debating an athiest? They don't believe in heaven. Duh!
A man dead in his sins (Ephesians 2) cannot understand spiritual things. It is useless to debate such with them. There is NO common ground with a lost person on these matters - how can one find it?
As Paul demonstrated on Mars Hill, we who are in Christ must declare Him to the lost world - not discuss ethereal issues of whether heathens can hold moral opinions.
Overall, I think Warren did much better than I've ever seen or heard him in the past.