Alma makes it clear that any in the congregation who persist in these actions are precisely the ones that the Lord has declared that they should be "hewn down and cast into the fire." Of course Alma leaves open the possibility of repentance, which is what he really wants.
Historical: The irony of this situation is that the coming events will have those who follow the church in greater danger of death by fire than the wicked. Clearly the Lord's declaration has a much more eternal perspective.