I agree that it is ridiculous that Christians think they can do whatever they want and sin because of grace ( which just shows they are not under grace )....but you have this taken out of complete context of what was being said...it's a common practice we have as people when we only "see" certain things.
Man your view of christianity is skewed if you truly believe that christians DON'T need to "bring forth any change" in our lives. The whole point of being a christian IS to produce fruitful changes in our lives!! ALL sin is unacceptable to God and will NOT get you into heaven unless they are repented of. Your statement of christians "being free to have affairs, get drunk, etc" is completely and utterly ridiculous..