فَمَنَعَتْهُ الْمُعْتَزِلَةُ بِنَاءً عَلَى الْقُبْحِ الْعَقْلِيِّ
The Muʿtazilah prohibited it on the basis of rational moral objection.
Their argument holds that charging an addressee with what they cannot perform lacks a proper moral justification and an attainable form of compliance. Reason therefore limits what can count as a fitting obligation.
Other theologians respond by asking precisely what “morally objectionable” means and how far human ethical classifications may be applied to divine action. The disagreement concerns not only the conclusion but the basis and definition of rational good and evil.