Does God condemn a person for rejecting Him ?  Or does an already damned person remain condemned when he rejects God ?

I believe it is the latter.  Unfortunately, the partly inaccurate and truncated message that people often hear is that they will go to hell for rejecting God.

This is what John 3 : 17 - 18 actually says –

For God did not send His Son [ Jesus ] to condemn the world, but to save the world through Him.  Whoever believes in Him [ ie. Jesus ] is not condemned, but whoever does not believe already stands condemned because he has not believed in the name of God’s one and only Son.

Paraphrased –

A drug is invented not to kill a patient, but to cure him.  A patient who takes his medicine gets better, but a patient who refuses to take his medicine is as good as dead, because he has not taken the only thing which can cure his otherwise terminal illness.

Josh has reached an age where he can play with his older brother, Jed.  Unfortunately, boys are hardly gentle at play and they still require quite a bit of supervision to make sure they don’t inadvertantly maul each other.