[unanswered]

It has to be done because of anti-discrimination laws.

Refuse to rent to someone who you met in person and is an obvious meth head who will totally trash the apartment they second they acquire it; who obviously has no job and will never pay rent? Well you "must" have learned of some protected characteristic too and therefore you just discriminated against them.

Refuse to rent to someone because "computer says no"? You're fine.