"You can't be moral without God."
Sure I can. You may not agree with my morals but I'd abide by them thus making me moral.
"Without God, there would be no morals."
Then why is there widely varying morals between people of different times/countries/regions/etc? Doesn't god give everyone the same morals?
"I could say that stealing is okay, while you despise it."
Yes, you certainly could. I would personally think it was immoral (barring certain circumstances) but you would think it was perfectly moral, thus making you a moral person in your own eyes.
Look, here's the point: morality is, essentially, subjective except for certain heinous acts that nearly everyone deems "immoral" and even then you're bound to find a handful who don't agree with that.
"This reminds me of an argument where an atheist tried to tell a Christian that it was wrong that men in the Bible who were not told otherwise would marry close relatives. The fact is, if you're an atheist, you can't believe in morals. Instead, you believe what you want to believe. So how can you judge others?"
I judge others by my own standards. Same as you. You simply get your ideals from a musty, dusty two thousand year old pile of moral bankruptcy whereas I tend to base my morals on the Golden Rule. As long as you're not hurting someone else you can do any fucking thing you want as far as I'm concerned.