The farce is the accusation that people think that way.
Jesus paid our sin debt in full.
There is nothing left for us to do in regard to attaining salvation.
Yes, there is stuff to be done in being conformed to the likeness of Christ.
Learning to operate in the mind of Christ and becoming more like Him everyday is what demands our taking up our cross as we learn to say no to the flesh and walk in the Spirit, but that does NOT affect our salvation, which is sealed in heaven by the Holy Spirit.
And the accusation that Christians think they can do what they want shows an abysmal ignorance of the teaching of Scripture and how a born again, born from above Christian really thinks. The Holy Spirit living in someone would never think that way.
While sin does not cost the saved person their salvation, that does not by any means mean that they can or will get away with it. God disciplines those He loves and since we are legitimate children, we will be disciplined for the sin we commit, but we will not be disowned (lose our salvation)
I have always said the most miserable person on earth, is not the lost, Hell bound sinner, but the born again, saved person who is straying from the straight and narrow, and gotten out of the fellowship that he/she knows they should be in. I have been there. I have gotten out of fellowship, and been under the heavy hand of God, in chastening. It was by far, the worst time in my life, as the Lord had to give a few raps across the knuckles, just to get my attention. It was not a fun time.