Well, I guess I am disputing that, too, lol. Just because I believe that God is the one that has endowed us with a sense of right or wrong doesn't mean I can't get why they think there can be right or wrong without God. It's quite simple, really. If there is no God, how could he have created right or wrong?
It's just the genesis of a circular argument, because each assumes the other's baseline is erroneous. It's basically an unwinnable one, unless you can get them to accept God in the first place. Or vice versa.
I disagree. You are free to make their case for them if you think it can be done.