You obviously want to handle this in your sons best interest so I believe it's reasonable to state at 6 years old he probably isn't consciously aware of what is motivating him as much as he's doing it because he likes the outcome.
I remember being taught that the age of reason is 7 years old (don't think that has changed). So in generalities he isn't reasoning his choice. When he does reason it, (despite double standards that may be obvious or not to your son) it will still boil down to his knowing the expectation is to do the right thing, and consequences will go a long way in helping him make better choices.
From my own experience, I think it is important that our children (ourselves included) believe that we have the power to do the right thing no matter what dysfunction is going on around us. I wouldn't bring AH into this unless your son does. I suspect your son will innocently say, "why can dad lie?" if he has an issue with it though again, I doubt he is even seeing it that way. A discussion about lying and son giving examples of someone who has lied will give you a bigger picture as well.