That response does... show you are thinking of it in terms of automatic righteousness that can never be lost. That's not what Paul taught. That instead is from some mystical idea created by men.
Look at the believer in 1 Corinthians 5 that was having sex with his own mother to see how Paul treated that one, and the church members there who didn't do their duty in casting that one out from among them.
1 Cor 5:1-6
5:1 It is reported commonly that there is fornication among you, and such fornication as is not so much as named among the Gentiles, that one should have his father's wife.
2 And ye are puffed up, and have not rather mourned, that he that hath done this deed might be taken away from among you.
3 For I verily, as absent in body, but present in spirit, have judged already, as though I were present, concerning him that hath so done this deed,
4 In the name of our Lord Jesus Christ, when ye are gathered together, and my spirit, with the power of our Lord Jesus Christ,
5 To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
6 Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump?
KJV
Why would Paul say, "...that the spirit may be saved in the day of the Lord Jesus"? I will tell you...
Our Lord Jesus warned us about being assigned to the "outer darkness" when He returns (Matt.8; Matt.22; Matt.25). That's not just about the non-believer, especially as He showed with the unprofitable servant example and the five foolish virgins of Matt.25.
In Revelation 22:14-15, we are shown the wicked in a place of separation outside the gates of the holy city, and that is for the time of Christ's 1,000 years reign (even though it's found written in Rev.22). That is the "outer darkness" He was talking about which is for that 1,000 years time.
That is where Paul was talking about for that believer who was having sex with his own mother, when he said that his spirit MAY be saved in the day of the Lord Jesus (i.e., the 1,000 years of Rev.20). In other words, by that person's act Paul cast him out, and was ready to be done with that sinner. Some suggest that sinner may have repented per hints in later Chapters and was accepted back into the congregation again. We don't know that for sure.
What is important is that Paul showed what can happen to a believer who practices such kind of immoral behavior. Paul was judging that one based on God's law, because that is where that kind of sin is shown to be an abomination to The LORD.
One of the problems with the hyper-grace movement is most of their preachers are not even aware of the events to take place in Christ's future 1,000 years reign involving believers on Him that fall away like that. They will be assigned to the place of separation where the wicked dead (spiritually dead) are in that time, and stand in judgment throughout the whole... 1,000 years (see Ezekiel 44). Those will not... be allowed to approach Jesus in that time.
Does that mean our Lord Jesus will forget that believer Paul cast out? No, of course not; but their status during the future 1,000 years is not going to be a happy time.