OK - I'll spell it out for you. The argument I was responding to appeared to be that no one should criticize any behavior, unreasonable, illegal or otherwise, if they had ever broken a law themselves. It's not uncommon for that argument to be asserted based on the biblical reference to casting the first stone. I was enquiring if that was the case.
In fact it is not a requirement to be completely ignorant of the bible, or any other religious text, in order not to be a believer. Some familiarity is actually very useful in debunking dogma. And yes - biblical references are quite common, as are other literary or cultural references, in normal conversation.