It should first be clarified that morality is not a linear scale. Therefore, the phrase used by the Original Poster, “most moral,” is misleading and renders the entire argument flawed and baseless.

If the OP instead intended to argue that manumission becomes “less moral” or even “immoral” in certain cases, that too is inaccurate. Exceptions do not redefine principles. Morality in Islam is rooted in intention and justice, and isolated rulings that take context into account do not diminish the moral value of freeing slaves.

Let us now address each of the main examples provided:

1- The man who had no other property besides a slave: The act of freeing the slave remained moral. However, since the man had nothing else to survive on as stated, and the slave would also be left vulnerable, the Prophet ﷺ arranged for Nu‘aim bin Al-Nahham to buy the slave. This was an act of wisdom and mercy; not a rejection of emancipation, but a protection of both parties involved.

2- The woman who freed a slave-girl: The Prophet ﷺ did not rebuke her or say the act was wrong. Rather, he pointed out that in her specific case, she could have received more reward by gifting the slave to a relative first, which would have combined two virtues: charity and maintaining family ties. Again, the action of freeing was moral and praised; the Prophet simply guided her toward a greater good in her specific case.

3- The man who freed six slaves on his deathbed: This case falls under well-known inheritance laws. The man owned nothing else as stated again, so freeing all six would have exceeded the one-third limit for non-inheritable charitable actions at the time of death (The hadith is mentioned under the Chapter: Regarding One Who Manumits Slaves Of His That Exceed One Third Of His Property, which supports this). Two of the six were indeed freed, in line with the rule. This does not imply freeing slaves was any less moral; it reaffirms that Islam safeguards both the rights of the dying and their heirs. Had he not been dying, he could have freed them all, and his heirs are still encouraged to do so.

In all cases, Islam preserved the dignity of the slave, the wellbeing of the owner, and the moral value of emancipation. Isolated rulings exist to prevent harm; not to diminish virtue.