You, evedentally, do not understand how sinful, by nature, that the regenerated man can be. Romans 1, It is the regenerated men, who God has manifested in them that which may be known of God. The regenerated men are holding the truth of those things that God made known to them, about himself, in unrighteousness. It is the regenerated men who are without excuse.
The natural man, as described in 1 Cor 2:14, cannot discern spiritual truths from a spiritual God., in order to hold spiritual truths in unrighteousness.