How Atheist Anti-Capitalists Miss the Point

If an economist sees the handiwork of God in the economy, does that invalidate his economic arguments from a secular perspective?

The great economist Ludwig von Mises, who himself was either atheist or agnostic, noted that:

Many economists, among them Adam Smith and Bastiat, believed in God. Hence they admired in the facts they had discovered the providential care of the great Director of Nature.' Atheist critics blame them for this attitude."