You just want to sin

This argument is made against atheists as an attempt to point out their (potential) fear of living the religious lifestyles, and is related to the accusation that atheists are just in denial.

The best ways to counter it are the following:

1. Ignore it; it's not really an argument to begin with

2. Agree to it with sarcasm; once again it's not an argument, or at least not a good one.

Theists sin all the time; their belief system is based on faith alone, or at least some of them believe that. Some of them claim that without religion there are no morals, even though there have been countless immoral acts done at the hands of religion. The Protestant Christian religion doesn't have regulations about being moral - to them you just have to pray your sins away, so in a sense, with religion there are still immoral things.

The Holocaust, Jihad, the Crusades, and the time of reform in Europe during and after the Middle Ages are fine examples of what harm religion can lead to.