Note: This article was originally written for the Path Treader Ministries Facebook page. Rather than fiddle around with the introduction, I have chosen to leave it mostly unedited. [Square brackets] signify the exceptions.
In my opinion, the only benefit to failing to study the word of God is that He judges the ignorant less harshly than the knowledgeable. One of many drawbacks of such failure is that we end up confusing warm and fuzzy feelings with a revelation from God.
Evidence of this can be seen in a relatively recent swarm of angry Liberals that came to this page. The purpose of [Path Treader Ministries was] to edify believers. I [had] no intention of debating, or even really reaching unbelievers with [that] page (though praise be to God if I can get someone saved). As such, when they tried to debate me, I told them that [Path Treader Ministries] is for Christians, and if they would like to debate, God Squad Apologetics was designed for them.
One of the heretics took issue with this. Is it very Christian to show preference to the Church? As a matter of fact, yes. Yes, it is. See, although God does love all people, He naturally shows preference to His children. What parent wouldn't? If you are a parent, imagine you see two children in equal need, but cannot attend both at the same time. One of them is your child, the other is not. We could even say perhaps it is a related child. A niece or nephew, maybe. To whom do you attend first?
The obvious answer is your own child. This does not mean that the other child is less valuable, it just means that your responsibility as a parent supersedes your responsibility as an aunt/uncle. Similarly, God not only favours His Church over those who refuse to join it, but encourages us to do likewise.
For example, through Paul, the Lord tells us to do good to all, especially to those of the household of faith. Do we do good to unbelievers? Absolutely. Woe betide you if you don't. But you can show preference to the believers.
Furthermore, we are actually commanded to shun false teachers. We're not only told to do good to Christians first, we aren't even supposed to welcome false teachers, because the welcome we give them is considered sharing in their evil.
Now, this does not mean we are to be particularly cruel to them. The Lord is perfectly capable of punishing false teachers by His own strength when the time comes. Believe me, He can pick and win His own fights, He does not need you. And indeed, there is nothing that says you literally cannot invite a false teacher into your home, offering them food and water, and sitting them down to say "now, about that false gospel of yours..." By all means, if you have the scriptural knowledge to do so, preferably with other fellow witnesses to help you, let them in and talk to them. But God, through John, sternly warns us: If you supply these people with anything that might help them spread their lies, you are guilty with them.
And so is it Biblical to divide the sheep from the goats? Let me put it this way: Goats. Have. Horns. (And yes, I'm aware that so do some sheep, don't take my metaphor too literally). It is absolutely Biblical to divide the sheep from the goats. Any mixture of believers and unbelievers runs the risk of injury to faith, and so it should always be done with wisdom. Do good to all, but don't think for one second that being a Christian requires you to be a doormat for all.