This statement does not have any biblical basis at all. If the gift of discerning the spirits is rare today, it is because the Word of God is rare today. Humanistic ideas and man-made doctrines have permeated Christendom. The Holy Spirit enables only those who wield the Sword of the Spirit -- the Word of God -- to discern the truth of God from the lies of Satan. The Scriptures themselves will give light to those who seek light. But those who are wilfully blind will then be judicially blinded.
Because thou sayest, I am rich, and increased with goods, and have need of nothing; and knowest not that thou art wretched, and miserable, and poor, and blind, and naked: (Rev. 3:17)
What? came the word of God out from you? or came it unto you only? If any man think himself to be a prophet, or spiritual, let him acknowledge that the things that I write unto you are the commandments of the Lord.
But if any man be ignorant, let him be ignorant. Wherefore, brethren, covet to prophesy, and forbid not to speak with tongues. Let all things be done decently and in order. (1 Cor. 14:36-40)
This I say therefore, and testify in the Lord, that ye henceforth walk not as other Gentiles walk, in the vanity of their mind, Having the understanding darkened, being alienated from the life of God through the ignorance that is in them,
because of the blindness of their heart: Who being past feeling have given themselves over unto lasciviousness, to work all uncleanness with greediness. But ye have not so learned Christ; If so be that ye have heard him, and have been taught by him, as the truth is in Jesus: That ye put off concerning the former conversation the old man, which is corrupt according to the deceitful lusts;
And be renewed in the spirit of your mind; And that ye put on the new man, which after God is created in righteousness and true holiness. (Eph. 4:17-24)
Willful blindness is to deny the existence of the gifts of the Spirit. The renewed Mind is what brings discernment via the Holy Ghost, every believer has a general sense of discernment. The Gift of discerning spirits is different in that this gift is visual.... a Seer as scripture calls them. We have a lot of prophets, Both true and false, very few seers. A Seer is someone called out of the womb with this gift. Like Samuel was. Or like Jeremiah. But this gift can also be granted to Believers, as Paul Speaks of. Do A study of the term seer in the old testament and find its equivalent in the new, You will find only one and that is the person who has the gift of discerning of spirits. This is both a negative gift, and a positive gift in that it does not just allow you to see fallacy but also verity. We have a lot of apologists using the vanity of their mind, and very few seers using the renewed spirit of the mind.
My OP is an overall observation of the church in general, whether fundamentalist or charismatic, Not a statement of biblical doctrine. I Agree, that truth comes by the word of God, But divine revelation comes via the Spirit of God, the mind of Christ.
It is time the church begins to learn how to fly on eagles wings instead of being grounded in human debates, and the doctrines of men.
But they that wait upon the LORD shall renew
their strength; they shall mount up with wings as eagles; they shall run, and not be weary;
and they shall walk, and not faint. (Isaiah 40:31)