The problem is that the vast majority who are fooled don't recognize the false doctrine when it's fed to them.
When I was a new Christian, I got caught up in the Word of Faith movement. Because men like Kenneth Copeland, the Happy Hunters, Larry Lea, etc, cloaked the false inside the true, I was easily fooled.
It would have done you no good to warn me about the danger of Copeland's teaching about the insufficiency of Christ's atonement (commonly known as the "Born Again Jesus" theory) because I was a new Christian and had not been discipled.
Jesus told us to beware of both false doctrines and wolves. I see no problem with naming the wolves.