I'm not sure what a "grace-hater" even is, but I surely don't understand how anyone can be presented with the following scriptural passages and not completely buy the doctrine of the perseverance of the saints (emphasis mine, and this is surely not anywhere close to an exhaustive list):
"Truly, truly, I say to you, whoever hears my word and believes Him Who sent Me has eternal life. He does not come into judgment, but has passed from death to life."
[John 5:24]
"For I have come down from heaven, not to do My own will but the will of Him Who sent me. And this is the will of Him Who sent Me, that I should lose nothing of all that He has given Me, but raise it up on the last day. For this is the will of My Father, that everyone who looks on the Son and believes in Him should have eternal life, and I will raise him up on the last day.”
[John 6:37-40]
"My sheep hear my voice, and I know them, and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. I and the Father are one.”
[John 10:27-30]
"And we know that for those who love God all things work together for good, for those who are called according to His purpose. For those whom He foreknew (foreloved) He also predestined to be conformed to the image of His Son, in order that He might be the firstborn among many brothers. And those whom He predestined He also called, and those whom He called He also justified, and those whom He justified He also glorified... Who shall separate us from the love of Christ?... (N)either death nor life, nor angels nor rulers, nor things present nor things to come, nor powers, nor height nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord."
[Romans 8:28-39]
In Him you also, when you heard the word of truth, the gospel of your salvation, and believed in Him, were sealed with the promised Holy Spirit, Who is the guarantee of our inheritance until we acquire possession of it, to the praise of His glory.
[Ephesians 1:13-14]
"...He who began a good work in you will bring it to completion at the day of Jesus Christ."
[Philippians 1:6]
"Blessed be the God and Father of our Lord Jesus Christ! According to His great mercy, He has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead, to an inheritance that is imperishable, undefiled, and unfading, kept in heaven for you, who by God’s power are being guarded through faith for a salvation ready to be revealed in the last time."
[1 Peter 1:3-5]
"Now to Him Who is able to keep you from stumbling and to present you blameless before the presence of his glory with great joy, to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever."
[Jude 24-25]
This argument, like most others, is really about "free will" and the supposed denial of it by John Calvin and folks who believe he was right (rather than Jacobus Arminius) about who does what in salvation. Neither Calvin nor people who understand scripture in the same way as he did ~ and Augustine (rather than Pelagius) and the other Reformers and so many since ~ surely do not deny human free will in any way, but only understand that, regarding God's salvation, human free will is in the context of God's sovereignty. As Paul says,
"...it depends not on human will or exertion, but on God, Who has mercy."
[Romans 9:16]
The implication is that humans do not not have free will ~ so they do indeed make a free choice regarding God's great salvation ~ but that it
depends on God's mercy and compassion and whether He extends it (conferring His salvation on the person via His Holy Spirit) or not. As Jesus Himself said,
"You did not choose Me, but I chose you and appointed you that you should go and bear fruit and that your fruit should abide, so that whatever you ask the Father in My name, He may give it to you."
[John 15:16]
And regarding those who "fall away," which is what we are talking about regarding whether perseverance of the saints is valid doctrine or not, those who do fall away were never really heart-regenerate Christians in the first place. As John says,
"(those who have fallen away) went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us."
[1 John 2:19]
Grace and peace to all.