Who's allowed to speak and heal in the name of Christ? Jesus was more inclusive than his disciples had thought to be.
Their need to be restrictive (in control?) was not the first time. The elders in Moses time had warned him that a non-elder was prophesying. Moses said they were limited if they thought God's power was so limited.
We still have difficulty in discerning who is speaking for the Lord.
Or, we still have difficulty in accepting that someone who isn't part of our own congregation can be connected with the Lord.
As a help, we could remember the words of Psalm 19--the judgments of the Lord are true, righteous, desirable. We should pay heed to them.
If we do pay attention to God's words and wisdom, then we can evaluate human words and wisdom. We can even pray the psalmist's prayer to be cleared of any movement away from those words and wisdom in our own ways.