You just want to sin
Theists who accuse atheists saying "you just want to sin," are suggesting that the atheist fears living with the moral requirements that come with religious belief. It is related to the accusation that atheists are just in denial, with the added implication that the denial is driven by hedonistic desires. This assertion is easy to counter.
This is not really an argument to begin with. Sin plays no role in people's atheism. The theist cannot reasonably deny your claim, as he or she has no access to your inner motivations.
"Although the most acute judges of the witches and even the witches themselves, were convinced of the guilt of witchery, the guilt nevertheless was non-existent. It is thus with all guilt."
The notion of sin is not universal among all theists or deists. For instance, you could well choose to be a deist, while still giving yourself the leeway to sin.
If maximizing hedonistic pleasure is the goal of an atheist, this desire would form a poor basis for him or her to reject a theistic religion that promises eternal bliss. After all, is an eternity of bliss not more hedonistic (pleasure-maximizing) than several decades of “sin”?
Equally facetious assertion can be made against apologists. Examples include, "You're not a Muslim because you just want to draw pictures of people," or “You’re not Amish because you just want to accumulate worldly possessions.”
Theists commit behaviors that various theistic traditions widely regard as sinful (e.g., excessive consumption of alcohol, cheating, theft, premarital sex, etc.). Of course, this fact does not invalidate arguments for theism, but it does point out that many forms of theism and “sin” are apparently compatible. In fact, the Protestant Christian religion holds that faith alone earns one a place in Heaven; no strict moral codes required!
One last thing to point out that this accusation seems to be analogous to a gang of thieves planning a heist in a zone continuously patrolled by (preferably competent) police officers, agreeing on "not believing" in the existence of said law-enforcers to be able to steal the goods without any hindrance. After all, if the non-theist truly believed deep inside that an omnipotent deity does exist and is watching, how would not believing in the existence/power of said deity actually hamper its ability to punish those who sin?