O, how some today need to review the Synod of Dordt as it speaks to the error of those who seek to divorce Christ's merit from man's salvation. Some atheists I've debated have set up a straw man by suggesting that "while God requires perfect righteousness for some (i.e., them) he simply substitutes or accepts "faith" from others" (i.e., believers) and therefore it "doesn't seem just or fair" (i.e., God must be an inconsistent judge).
Note the relation the Synod of Dordt draws:
Rejection of the Errors
Having set forth the orthodox teaching, the Synod rejects the errors of
those ... Who teach that what is involved in the new covenant of grace which God
the Father made with men through the intervening of Christ's death is not that
we are justified before God and saved through faith, insofar as it accepts
Christ's merit, but rather that God, having withdrawn his demand for perfect
obedience to the law, counts faith itself, and the imperfect obedience of
faith, as perfect obedience to the law, and graciously looks upon this as
worthy of the reward of eternal life.
For they contradict Scripture: "They are justified freely by his grace
through the redemption that came by Jesus Christ, whom God presented as a
sacrifice of atonement, through faith in his blood" (Rom. 3:24-25).