Why is 'Free Will' an offense to grace?

Another debater asked...

READER>> I interpret your statement[s] to mean "That [believing in free will] is an offense to God in that it does a disservice of some sort to His grace." Why does it?

ME>> Claiming that free will made a distinction between you and another rather than grace is not really a disservice to God's grace, for ultimately nothing interrupts God's service and purpose, even our unbelief. But instead it is a dishonoring of God and a prideful boast toward our fellowman.

Yet you ask a good question.

Why is belief in free will an offense to God?  First, the Scriptures themselves specifically teach that attributing spiritual progress to anything but grace is contemptible in Romans 2:4 and boastful in 1 Corinthians 4:7.  Second, I have also said that if we believe persuasion at the natural level of logic and argument is sufficient, then our evangelism will create victims rather than converts.  We will neglect to pray asking God to provide the heart change that only he can provide.  One might argue that we chose to pray because of our free will choice to obey.  However, Paul gives the glory for all his effort to God in 1 Corinthians 15:10 and even our prayers as explained in Romans 8:26.  Third, you have already admitted that there are no Scriptures that explicitly teach that man has a free will, but there are verses that teach that man is spiritually dead and must be regenerated by the Holy Spirit to be alive to God.  Since this is the case, the question begs: why not humbly accept the Scriptures?  Why the resistance?  Stubborn pride, perhaps?  Fourth, if I claim that my free will made the difference in my spiritual progress, I have a boast before my fellowman; but if I acknowledge that grace made the difference, I am God's servant to point others to the only hope for their healing, God himself. Furthermore, then God can answer for himself as to why he chooses to do this or that.

READER>> To my mind it is the Calvinist's perspective which does the disservice to God's grace by limiting it to a select few.

On that we totally agree, for God's love it not limited to a subset of mankind as Calvinists ignorantly teach.

READER>> or for the deterministic universalist, by rationing God's grace to a select few now and delaying His gift to a much later time for the others.

Yes, I can understand your concern.  However, I have also said I do not like the negative connotation of the word "deterministic."  The word ruins the artistry of what God is building and designing.  Yet I also ask with you, why did God bring me to faith at age 18, others earlier, and even others later?  Or why do many die in unbelief and suffer in Hades when God's grace could stem the tide?  I do not like these facts either.  However, it is what the Scriptures teach.  So we could try to find an explanation that makes sense to human reason alone and helps us feel more comfortable, or we could give our lives to the Spirit's purposes and allow God to make his appeal through us as Paul did in 2 Corinthians 5:20 (WEB): "We are therefore ambassadors on behalf of Christ, as though God were entreating by us: we beg you on behalf of Christ, be reconciled to God."

The mistake many make who reject God's sovereignty is imagining Him sitting in heaven pulling switches and using words like "deterministic" to describe his sovereign influence.  This is a mistake that improperly characterizes the beautiful work of God's grace.  God's sovereign grace is intimate and present and at work and when we obey his will then it is certain that he is at work through us for the good.