The point of “The fool says in his heart, ‘There is no God’” is that it is an impious, sinful heart that will deny God. The atheist’s denial flies in the face of much evidence to the contrary, including his own conscience and the universe he lives in.
A lack of evidence of God’s existence is not the true reason atheists reject a belief in God. Their rejection is due to a desire to live free of the moral constraints God requires and to escape the guilt that accompanies the violation of those constraints. “The wrath of God is being revealed from heaven against all the godlessness and wickedness of people, who suppress the truth by their wickedness, since what may be known about God is plain to them . . . so that people are without excuse. . . . Their thinking became futile and their foolish hearts were darkened. Although they claimed to be wise, they became fools. . . . Therefore God gave them over in the sinful desires of their hearts. . . . They exchanged the truth about God for a lie” (Romans 1:18–25).
Only fools don’t believe in God