It's a bit of a puzzle in it's self. In verse 4 the first thing he does is warn them that it would be easy to deceive them because of what they were asking. Then is something else puzzling to me in verse 5 about those doing the deceiving
Matthew 24 Interlinear Bible ...
What do you see him as saying in verse 5 is he saying that they would say "they were the Christ" or would they come and say that "Jesus was the Christ and deceive many"?
Jesus quoted what the deceivers would say concerning themselves.
Namely...Iam Christ.
Note: that is the spirit of antichrist, and it is found in the new age teachings.
To discern new age teachings in the churches all we essentially need to understand about those teachings is that they take the things that are found in the body of Christ and simply apply them as if they exist outside the body of Christ.
Thus the spirit of antichrist denies that Jesus Christ came in the flesh.
That is, they deny that Jesus is the only begotten Son of God.
For, if they confessed that Jesus of Nazareth is the only begotten Son of God, in whom God is well pleased, then they can't reason they are, as they claim to be, christs also.
However, it can be a bit harder to recognize the antichrist spirit in the churches because they present the "Iam Christ" lie initially by claiming to be anointed of God.
They fail to teach that the anointing of God is upon the head of Jesus, and not upon the head of another man.
As I said, they take the things that belong only to Jesus, and apply it themselves, outside the body of Christ.
Consider the doctrine of Simon the Magician.