One of the most chilling passages I've ever seen in the Bible is Matthew 7:22-23: "Many will say to Me on that day, 'Lord, Lord, did we not prophesy in Your name, and in your name cast out demons, and in Your name perform many miracles?' And then I will declare to them,'I never knew you; depart from Me, you who practice lawlessness.' "(NASB)
At the end of the Sermon on the Mount, Jesus is talking about the Judgment Day. And those whom He describes Himself saying this to are not the pagans, the atheists, the hardened sinners--He will be saying this to people who thought they amounted to something in the church, people who did miracles and wonders in His name. He calls them "you who practice lawlessness." What is "lawlessness"? It's rejecting God's law; and Jesus elsewhere summed up the whole law in two things: Love God, and love your neighbor as yourself. In other words, he is effectively saying, if you don't walk in love for God and man, you are none of Mine, and no religious activity, even miracle-working, can overcome that lack.
This passage is not an isolated one-time thing; it is echoed through the rest of the NT. Just before His arrest, Jesus was saying things to the disciples like "Love one another as I have loved you" and "By this all men will know you are my disciples, if you love one another." Late in his life John was writing things like "If any man does not love his brother, the love of the Father is not in him" and "If you do not love your brother that you do see, how can you love God who you do not see." Paul wrote a whole chapter on love in I Cor. 13, and started out by saying it was "a more excellent way" than the tongues and prophesying he had just written about. One more from John: "For love is of God, and every one who loves is born of God, and knows God." And that implies that those who do not love do not know God.
In my life I've run across a lot of Christians who are more interested in arguing than in love--arguing over End Times, whether the "sign gifts" have ceased or not, Calvinism/Arminianism, liberal theology/conservative theology (there seems to be a whole cottage industry these days of blogs and websites to identify who is orthodox and who's a heretic) and nowadays over the postmodern thing--I see quite a few who are "agin" it. And if there's one thing I've seen again and again over the years, it's that when people start arguing they quit loving. I've seen at least one church destroyed because the leaders argued instead of loving.
I'm not saying these other issues have no importance at all. But it seems clear to me that Jesus, John, and Paul all considered Love the Most Important Thing. And any time we take one of these lesser things and try to act like it's the Most Important and forget that Love is the real Most Important Thing, we are making our own priorities higher than God's, and are in danger of the final rejection of Matthew 7:23.