elohiym believes.... (correct me if I am wrong) that when a person becomes a Christian they receive a new nature...
Yup!
2Cor 5:17 Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
Has your old man, the sinner, passed away, Knight? Or is he still busy sinning when he gets the chance? If he's busy sinning then the old has not passed away in your life, and you have not become new.
...and because of that new nature they will live perfectly the rest of their life.
That's the crux of our difference, Knight. You don't understand what it means to live perfectly in the spirit because you are focused on the flesh. Flesh can NEVER be perfected, but our spirit IS perfect.
John 3:6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
Gal 3:3 Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?
Php 3:3 For we are the circumcision, which worship God in the spirit, and rejoice in Christ Jesus, and have no confidence in the flesh.
Gal 5:16 This I say then, Walk in the Spirit, and
ye shall not fulfil the lust of the flesh.
If you fulfill the lusts of the flesh (sin) it can ONLY mean that you are not walking in the spirit.
If they do sin, they were never a Christian to begin with.
Yup! It's evidence that they aren't converted, but are still carnal. They don't get it yet.
Gal 2:17-18 But if, while we seek to be justified by Christ, we ourselves also are found sinners, is therefore Christ the minister of sin? God forbid. For if I build again the things which I destroyed, I make myself a transgressor.