The most pastoral and straightforward refutation of "Sinless Perfectionism" I have been able to find is from pastor and author Randy Alcorn. I'm thankful for the thorough and thoughtful video posted HERE on the Eternal Perspectives website.
CLICK HERE FOR VIDEO & TRANSCRIPT
An excerpt from the transcript...
Can a believer sin? Yes. Should a believer sin? No. Has God given us in Christ the resources so that we can turn from sin and live a life that is righteous and holy before Him? Absolutely, yes! We are new creations in Christ, and as we see in Titus 2, the grace of God teaches us to say no to ungodliness. 1 Corinthians 10:13 says we face no temptation or trial that does not offer an escape for the fully yielded Christian.
We should never be content with our sin or excuse ourselves from it. Rather, we should be quick to recognize our sin, so that we can confess it and keep it from entangling us. There is no more certain way to be entangled by sin than to keep telling yourself what you’re doing really isn’t sin at all.
My concern for people who truly believe in sinless perfectionism, is not simply that they’re kidding themselves. It’s something worse—what are they going to do about the sin in their lives they don’t see? They are going to end up redefining sin, denying sin, justifying their sin, and playing dangerous games by calling their sins by different and less serious names.
To call their sins mere mistakes is to minimize their sins, and to keep them from obeying the commands to confess their sins to one another and to God. Where is the humility in that? Ironically, the mother of all sins is the sin of pride. What could more effectively instill a sense of pride than to believe we are incapable of sinning? To admit we are dead wrong is an act of humility we should practice regularly. But this can’t be done by someone whose theology tells them they cannot sin.