The Christianity Jesus came to prepare man to have is a real and personal relationship with God. The term Christian actually means a person who is "anointed" by Christ. This anointing means that the believer is "set apart", and made "holy" by Jesus Christ with the Holy Spirit. This experience happens when that person believes His instruction to be "Born Again" by baptism in water, and receives the Holy Spirit (John 3:5-7, Acts 2:37,38). It is only when a person is Born Again that person is adopted to become the son or daughter of God (Romans 8:15,16).
Only then we are now able to understand and relate to God, who is a Spirit. We do not have the capacity to relate to His type of love before we receive the Holy Spirit (I John4:10,19, Rom.5:5). Only when that relationship and love is established will a real change take place in the believer's behaviour. This is known as "walking in the Spirit". God changes us from the inside. That is when His moral code governs us and will be evident in that person's value system and conduct.
Therefore, Christianity is not a "religion", a person does not become a "Christian" because he or she observes some moral code of behaviour or goes through some ritual, or celebrates Christmas. When we don't understand the significance of this we might compare "Christians" by the moral codes of other religions.
The bible tells us that a person who has not been given the 10 Commandments, can and do have a "law" [code of conscience] to themselves Rom.2:14,15. This is what humanism is.
The problem here is that no one can really live up to ALL the requirements of those commandments, whether specified by God or otherwise.Rom.3:23. Therefore, there is no objective justification. No one can really say he is better than other people, or that God should give one person more merit than another.
Only God is Just and Sovereign. He is no respecter of persons. A believer has to submit to His code (law) of right and wrong, fair and just. Eventually, everyone will have to whether they believe in him or not? Even when a person does not want to believe in God, that person is still subject to His "laws" that govern life, death and final judgement.