Yes, the issue of Jesus Christ.
Why do we confront? Because our Lord confronted the teachers of religion in His earthly ministry. Notice, He never argued, He simply declared the Truth that He is. Note too, He didn’t establish a new religion. He was born into Judaism, accepted it for what it was, and then Himself replaced it. No more religion, only Jesus.
Though it is given to some in the Body of Christ to controversy and polemics, it is not my place, though I sometimes am driven to it.
If argument were the major means to bring people to Christ, the world would all be Christian by now, but it isn't. In former days, if a man was bested in an argument, he knew it, and gave in. Nowadays, we have been so trained to accept moral and religious relativism, that even when we've been proven wrong, we cling to outdated and outlandish notions. Why? Simply because they're ours, and there's no punishment for it.
We who have received only what Jesus Christ and His holy apostles handed over to us can never accept another gospel. When we hear holy apostle Paul warning us, ‘If anyone preaches a version of the good news different from the one we have already preached to you, whether it be ourselves or an angel from heaven, he is to be condemned’ (Galatians 1:8), we know that the enemy of mankind will plant such false religions in two ways: through false apostles inside the Church, and through angelic beings outside the Church.
We know that both Muhammad and Joseph Smith Jr received their revelations from angels (and there have been others, less successful and therefore less well-known), which to me fulfills the words of the holy apostle. But the corruption of evangelical doctrine also happens within the Church through the accretions of the Roman popes and others, even down to modern times, even while claiming to be evangelical. These are who the apostle was referring to, I believe, when he writes ‘whether it be ourselves.’
As an Orthodox Christian and disciple of Jesus, I willingly fellowship with all who believe in Him as Lord and Savior and God-man, even when they don't use the exact catch words that I use: I can see through the semantics and the cosmetics. But when I meet those who say they believe in Jesus but reserve for themselves, and exclude me from, some special qualification that puts them on a higher or better level than me, well, I get the whiff of bad angels' breath and the smell of stale altar cloths, if you know what I mean.
Anyone who confesses Christ belongs in the Church, but only if they leave their fairytales behind, and since they won't, they don't. They drew the imaginary line that they won't cross, and there's nothing we can do to change that.
Only grace can convert the heart of man.