There are Two Kingdoms
Jesus stated the principle that a kingdom would not attack itself. Since Satan would not attack Satan, Jesus did not cast out demons by the power of demons. But there are two kingdoms, and the principle applies to both of them. Satan would not attack himself, and neither would God attack himself.
Therefore, those who attack God must not belong to the kingdom of God. They must belong to the only other kingdom, the kingdom of Satan. And this means that those who attack such things like healing the sick and speaking in tongues, which belong to the kingdom of God, must themselves belong to the kingdom of Satan.
In the same context, Jesus also said, “Whoever is not with me is against me, and whoever does not gather with me scatters.” It is not enough to avoid speaking against healing the sick and speaking in tongues. To be counted among those who stand with Jesus, a person must actively endorse healing the sick and speaking in tongues. He must make it his mission to “gather” people for healing the sick and speaking in tongues, for casting out demons, for prophecy, and all other kinds of signs and wonders.