I guy can say something dumb and still be a Christian. Denying the Doctrines of Grace isn't the sin against the Holy Spirit. Someone can say something dumb and believe something dumb and that's generally not enough to condemn them to Hell. To say Christ was just a good man and I'm trusting in the Golden Rule for my salvation is one thing, but to (as Rich pointed out) reach a probably temporary wrong conclusion about the nature of God based in really flawed reasoning isn't enough evidence to write him or her off as a non-Christian.

Now as to what you would say to them? I'm going through something similar with a family member, and I was given some good advice. That was "If someone has reached a decision without using logic, you can't change their decision using logic". I'm still digesting that, but perhaps it will give you food for thought.

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Tim Vaughan, 48 years old, member Redeemer OPC, Santa Maria CA.