Hi English Rose,
1. I think your friend is making the right choice in leaving his fellowship over "NCT".
2. You can read about "NCT" here:
Theopedia: New Covenant Theology.
3. One of the major tenets of NCT is that the Ten Commandments, in fact ALL of the OT law was abolished at the coming of Christ and therefore not binding upon Christians today...
except and
unless Christ Himself or an apostle teaches that a particular law, including any/all of the Ten Commandments is to be observed. This is why adherents of NCT reject the 4th Commandment concerning the Sabbath and believe it is not binding today.
4. There are many passages which one could use to refute this entire idea that there are "two laws" in Scripture; the law of the Old Testament which is abrogated in its entirety, including the moral law, and 2) the "Law of Christ" which alone pertains to New Testament (Church) Christians. For example, Matt 5:17-19; Lk 21:33; Jh 7:16; 14:10; 17:8,14,17; Rom 7:7,12,14,22,25; 1Tim 1:8; Heb 12:21-26.
Now, what is most instructive is this last reference, Hebrews 12:21-26 where the inspired author takes us back to Mt. Sinai and the giving of the law to Moses. He mentions that "voice" that they heard that "spoke on earth" and then again who shall "speak from heaven". This passage in the Greek makes clear that the one who spoke on Mt. Sinai and who shall once again speak from heaven is none other than Christ; the pre-incarnate Christ on Sinai and the now glorified Christ Who sits on the right hand of the Father in heaven. When we use the "Analogy of Faith", comparing Scripture with Scripture, e.g., comparing the above referenced passages, it becomes very clear that Christ is the Giver of the law in all times and thus it is one and the same. There is not an OT law and a new and different NT law. For God Himself is the author of the moral law, that being an expression of His very nature. Once cannot therefore bifurcate the moral law given on Sinai from a new version with additions and subtractions allegedly given by Christ in the NT to the Church.
I hope this helps to give you a beginning for understanding this error being promoted as New Covenant Theology (NCT).

In His grace,