Yes, we do face a threat from false teachers. But way too much energy is expended on trying to prove unprovable doctrinal positions. The greatest enemy of the Church is not confusion over election/free will/God's sovereignty and such. It's the divisiveness that such arguments can cause. Some of the great men of God had a falling out over the Rapture theology. Who knows? Who cares? Well, many do care and it is folly. No one know for sure. Pre, Post, No-trib? We will find out one day.
God commands a blessing where the brethren dwell in unity. That does not mean a unity in doctrine. I teach baptism by immersion. It's a no-brainer for me. Yet other happily sprinkle infants. They have a doctrinal basis for doing that. My fellowship with a believer is based on the unity of the Spirit and in love for the brethren. Seriously, it is possible to agree to disagree on many issues. Satan loves to see Christians getting mad at each other. He knows how much it weakens the church.
There are non-negotiable truths that make Christianity what it is. Other than that, I don't believe that we need to fight each other. Save the energy for fighting the real enemy of our souls.