If man loses the first commandment, he really loses. If the first command holds no weight then God is not that glorious and there is no redemption.
Rail against this command and it means that either God is one of many or He is indifferent to how one thinks of him and therefore isn’t that big of a deal. If God is one of many, or there is no God at all this spells nothing less than the death of ultimate meaning, moral absolutes, ultimate truth, and purpose. On the other hand, if the one God is indifferent to how we worship Him, He isn’t that big of a deal. You might say that He is loving and accepts all worship, but love is jealous. Try praising your spouse with compliments that are only true of someone else. Tell her how you love her big brown eyes when they’re blue and see how that goes. Evidently truth matters. The deepest kinds of love are rooted in truth. God’s love gives us Himself, and it gives us the truth about Himself.
If this command doesn’t stand, it means there is not a God glorious and loving, personal and holy, revealing Himself to man as man’s greatest joy. Lose the exclusivity of God, and you lose glory.
Further, if this command is a spurious, then there is no redemption. What are we to do with our guilt? If there is a Savior who has borne away our sins and clothes us in His righteousness then He has total claim on us.
Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body. Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body (1 Corinthians 6:18–20 ESV).
Lose the exclusivity of God, and you forfeit a God unrivaled in glory bringing us into the enjoyment of Himself by unsurpassed sacrificial love. More lovers doesn’t mean more love.