The same argument comes up in atheism-- "if you don't believe in [eternal damnation], what stops you from just killing people indiscriminately?" It reflects the sad state of the asker's moral compass.
Same with Catholics and confession-- another broken system in which you are free to sin arbitrarily through confession and repentance. The point of the doctrine itself is to transcend the cycle and be better than that. (I know little about it but I'm told there is a similar mechanism in Hinduism re: karma.)
Fear of god/state/consequence keeps people in line, but it's a failsafe, not the governor. The only thing preventing fraud in your tribe should not be the intangible threat of later consequence from a greater authority. You're supposed to respect each other enough to not prey on your own kind.
Another take is looking at crimes like CSA. The state punishes it when it is brought to their attention, but that does not absolve the community from necessarily participating in its policing ahead of that-- the community are the ones best positioned to detect, intervene, and enforce social norms around it in the first place.