That speaks more to me about judging where the fruit comes from, whether the Spirit or the flesh, not the judgment of the individual
Mat 7:20 Wherefore by their fruits ye shall know them
It refers knowing the person BY their fruits that they produce, not where they gathered it from. It even goes further and explains this with these verses:
Mat 7:21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
Mat 7:22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
Mat 7:23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
These are those people that had evil fruits. It doesnt' speak to where they gathered them from. It is speaking to what they do.