Why debate Calvinism?

Since your salvation doesn't hinge on whether or not you believe in Calvinism, what's the point of debating Calvinism? What practical difference does it make whether you're a freewill theist or Calvinist?

As a matter of fact, it is possible to become obsessed with this debate to the exclusion of other important issues. It shouldn't be all about Calvinism all the time. That said, the difference has practical consequences:

1. Theological positions tend to develop internally to the point of taking their assumptions to their logical extreme:

i) Open theism resolves the tension between freewill and foreknowledge by ditching foreknowledge. But how can you trust a God who's in the dark about the future? How can you trust a God who gambles with human lives? 

ii) There's often a shift from exclusivism to inclusivism. If God loves everyone, wants everyone to be saved, made provision for everyone to be saved, how's that consistent with restricted opportunities to take advantage of that provision? What about those who never heard the Gospel? Inclusivism logically demotes the urgency of missions and evangelism. 

iii) Apropos (ii), this life isn't an even playing field. Spiritual opportunities vary drastically. That nudges freewill theism towards postmortem evangelism/conversion. And that, again, logically demotes the urgency of missions and evangelism. 

2. Freewill theists sometimes alleged the predestination negates petitionary prayer. If true, that's a very practical issue. Conversely, open theists argue that divine foreknowledge is providentially useless because it's too late for God to intervene. If so, that would negate petitionary prayer. 

3. Calvinism and freewill theism will give some different answers to the problem of evil. And that's a pastoral issue as well as a philosophical issue. Some theodicies can be adapted to Calvinism and freewill theism alike, but other theodicies pair off with Calvinism or freewill theism.

4. Freewill theism may erode inerrancy and commitment to biblical authority by appealing to moral intuitions that trump the witness of Scripture in case of conflict. There are freewill theists who admit that if Scripture taught Calvinism, then they choose their moral intuitions over Scripture. They repudiate the God of Scripture in that event. 

Another example is that some freewill theists reject OT theism for the same reason they reject Reformed theism: they think the Calvinist God is too harsh, and they think Yahweh is too harsh.  

5. Apropos (4), some freewill theists seem to think Calvinism is worse than atheism. So what's their fallback if they lose confidence in freewill theism? Since Calvinism is not an option, do they land in atheism?

6. Views on the necessary preconditions of moral responsibility can impact law and social policy:

i) If homosexuals don't actually choose their "orientation," then that's exculpatory in case libertarian freedom is a necessary precondition for moral responsibility. So it would be unfair to discriminate against homosexuals in any respect. 

Same with gender dysphoria. They ought to be accommodated if they didn't choose it.

ii) The insanity defense takes libertarian freedom for granted. If you're too evil to know the difference between good and evil, that's exculpatory. If you can't help yourself because the urges are overpowering, that's exculpatory. 

7. A common objection to Calvinism is that a Calvinist can't tell everyone "God loves you!" But does everyone need to think that God loves them, or is that presumptuous? There are hardened sinners who believe God loves them because they have such a high opinion of themselves. How could God not love such a wonderful person as themselves! They'd benefit from being told that maybe God doesn't love them. They need to be shaken out of their complacency.

8. Freewill theists are more likely to reject penal substitution. That impacts how we preach the Gospel. 

9. Although all classic Protestants subscribe to sola fide, Calvinists have a way of unpacking the concept in terms of a threefold imputation. That has more explanatory power than a bare affirmation of sola fide. 

10. Traditional Catholicism has radically different views of how God saves people. Saving grace is mediated by the sacraments, which are mediated by the priesthood. Likewise, the intercession of the saints. That's a different theological paradigm than Calvinism. Are you putting your faith in Jesus for salvation-or Mary? Or a wafer? Or priestly absolution? If you're wrong, that makes a practical difference. Conversely, post-Vatican II theology is edging towards universalism. That, too, is a different theological paradigm than Calvinism. If you're wrong, that makes a practical difference. 

11. When a Calvinism debates a classical Arminian or Lutheran, they take Protestant essentials for granted. But when a Calvinist debates a Catholic, then the contrast involves divergent views on a wider range of issues, like the locus of interpretation. 

12. Christians have to believe something. They can't leave all the blanks unfilled. Although they can suspend judgment on some controversies, they must takes sides on some issues. Otherwise, their faith is a cipher. So the debate over Calvinism is part of that larger demand.