Quote me one verse where it says owning a slave even for 5 minutes is utterly immoral and unethical.
We should hold religious books that are suppose to guide all of humanity to a higher standard shouldn't we?
In Islam, freeing slaves is a way of expiations of sins. Also Zakat is a compulsory pillar of Islam and even there we find a mention of giving money to those people who were facing slavery. And this is 1400 years before not a recent phenomenon like USA 1861 civil war.
This category of people is defined in surah at-Taubah (9) verse 60:
“The alms are only for the poor and the needy, and those who collect them, and those whose hearts are to be reconciled, and to free the captives and the debtors, and for the cause of Allah, and (for) the wayfarers; a duty imposed by Allah. Allah is knower, Wise.” (The Holy Qur’an 9:60).
Zakat is distributed among 8 asnaf (categories) of people, namely:
Fakir – One who has neither material possessions nor means of livelihood.
Miskin – One with insufficient means of livelihood to meet basic needs.
Amil – One who is appointed to collect zakat.
Muallaf – One who converts to Islam.
Riqab – One who wants to free himself from bondage or the shackles of slavery.
Gharmin – One who is in debt (money borrowed to meet basic, halal expenditure).
Fisabillillah – One who fights for the cause of Allah.
Ibnus Sabil – One who is stranded in journey.
Source: Surah Taubah, Holy Quran