Those last six words "in the absence of a crowd" don't sound like much but when you think about it you see how we are all that way when thinking about doing something we know is wrong. Once we consent to betrayal we want to carry it out in secret where no one can see us as if that makes it less wrong or sinful. People even say worthless things like, "Well, we are consenting adults" as if that makes sin not sin. For the record, only God gets to define sin and He defines it in terms of who it is against (Him) instead of who you do it with.
When you act as if the Cup was empty you create a society, culture and generations to come which are based on our will not God’s will and as liberating as that sounds once the dust from the latest parade settles you will have to face the consequences of the way you have handled the Cup. The most debilitating being that you have created a world in which there is no higher authority to appeal to for help, redemption, forgiveness or liberation from sin and the injustice of a fallen world. If the Cup is empty then there is no sin to be forgiven, no standard of truth to which we can all appeal and no right and wrong.