Well, when he teaches that 1 John 1:9 was not written to Christians and that after one is born again it is wrong (I heard someone say he now claims a sin) to ask for forgiveness after one becomes born again... which is heresy because the Word very clearly teaches we are not without sin. You guys know 1 John 1:8 - If we say that we have no sin, we deceive ourselves, and the truth is not in us. Mr Prince claims this is a part of the Bible that was not written to Christians!
Another area of false teaching he is involved with it he claims, as do many extreme grace teachers, that the Holy Spirit never ever speaks to us about our short comings which is not what Jesus said in John 15 about the Father seeking to purge us so we bear more fruit, nor what the Lord said thru Paul in Hebrews that if we do not accept His correction we are illegitimate.
These are two very deceptive traps of satan to not engage Jesus in His High Priestly ministry when we sin as mentioned in Isaiah 55:7, and Proverbs 28:13
Extreme grace teachings has led to many growing cold in their relationship with the Lord since after all... as many extreme grace teachers teach, why spend time in prayer? Why spend time in the word? Spiritual growth? Why, that's nothing more than behavioral modification.
This is all just a step shy of universalism. Extreme grace teachers often cite legalism, their favorite terms for those that do not embrace their error, so they end up taking people to the ditch on the other side of the road as their message is not balanced (many of the hate the B word) and certainly is not full gospel as they leave much of the New Testament out of their message and some have the gall to say Jesus' teachings only apply to Jews who followed Him before He went to the Cross... so for many, the teachings of Jesus Christ is out.
Jesus said wisdom is justified by her children speaking of we can tell if wisdom being taught is good or not by the fruit that it bears... extreme grace has brought forth exactly what the Bible teaches will happen in the end times is that there will be a great falling away and men will be lovers of themselves before lovers of God and so, many today that say their are Christians put themselves before God and are engaging in "do what thou wilt" which is something that was made popular by the satanist alister crowley a teacher of hedonism which controls much of our society today and has krept in to the Body of Christ in a large way thanks to false teachers like Mr Prince.
A major telling sign is that he doesn't teach much on Romans 8:13 - For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.... since he doesn't really believe or teach on self control since his view is no matter how Christians live, they will go to Heaven.
Jesus specifically said not everyone who calls Him Lord will enter the Kingdom of God, so we will see in the end that so called "extreme grace" is in fact an infiltration of satan into the Body of Christ and it has been very effective thus far.