Salam alaikum.

Zanadigah from rafidah wrote:

We read in Sunan al-Kubra by Imam Beyhaqi:
عن نافع ، عن ابن عمر ” أنه كان إذا اشترى جارية كشف عن ساقها ووضع يده بين ثدييها و على عجزها
Nafe’e narrated that whenever Ibn Umar wanted to buy a slave-girl, he would inspect her by analysing her legs and placing his hands between her breasts and on her buttocks”

And here the answer to that assault:

The word used here is “jariya.” Jariya refers to a very young girl that has the ability to run around, not even a girl who attained puberty. These are the very same words that were used for the Mother of the Believers `A’isha (ra) five years before the hijra.
Perhaps the Shi`is would now say that she was a slave-girl too? For it is well known that for their lies to be considered true, they even belie the truth!
What is wrong in looking at a little girl or even checking her body to assure her faultlessness as a girl that would work as a servant?
This wasn’t simply the act of Ibn `Umar (ra), rather the Shi`is should check their works as well.
It is narrated in the authoritative Shi`i text Qurb al-Isnad [103] concerning Imam `Ali (ra):

أنه كان إذا أراد أن يشتري الجارية يكشف عن ساقيها فينظر إليها

“Whenever he [`Ali] intended to buy a jariya, he used to uncover her legs and look at them.”

And this report is declared reliable [mu`tabira] by Grand Ayatullah Abu al-Qasim al-Khu’i in Kitab al-Nikah [1:33]
What should the “appeal to justice” be now? Are you going to make fun of your own Imam and portray him as “no better” than a person who defame the most?
The act of Ibn `Umar (ra) has no aphrodisiacal side to it as our Imami Shi`i friends love to believe. A jariya or a little girl was checked not so one can fulfil their desires right in front of hundreds of marketers, but to see whether the girl suffers through any deficiencies and injuries or not, so she could serve with proficiency and be a good working servant.
This is further cleared from another Sahih narration right before the one you quoted from in Irwa al-Ghalil [6:201]:

أن ابن عمر كان يضع يده بين ثدييها ( يعني الجارية ) وعلى عجزها من فوق الثياب ويكشف عن ساقها
“Ibn `Umar (ra) used to put his hand between her [meaning the jariya’s] breasts and on her haunch from above (her) clothes and used to unveil her leg.”

Now the question is, if Ibn `Umar (ra) really was doing what the Shi`is think he was doing, then why did he choose to unveil her leg and not her chest and haunch?
The answer is simple. Because the bones and muscle between the breasts [sternum, ribs, etc.] and the haunch [pelvis, etc.] can be checked with the clothes on, but the disfigurement of legs or anything related to it would require the uncovering of the legs since women in those days wore long coverings, not pants.
The purpose for procuring such women was not molestation or enjoyment [mut`a] with them in marketplaces. Rather to free them from the trade market and provide them with an Islamic atmosphere, so they could understand the wisdom behind Islam and accept it.
The issue of slavery is a sensitive one. Normally, the view in an average secularist’s eyes is nothing but a fragment of imagination; such as chains, ill-treatment, hostility, discrimination, or even nudity. But when we say “slave” we mean bond servants, not the slaves kept by the English.
Who are treated in the same manner others are. As stated in the Qur’an:

“Worship Allah, and do not associate with Him anything, and be good to parents and to kinsmen and orphans and the needy and the close neighbor and the distant neighbor and the companion at your side and the wayfarer and to those (slaves who are) owned by you. Surely, Allah does not like those who are arrogant, proud, those who are miserly and bid people to be miserly, and conceal what Allah has given them of His grace – and We have prepared for the disbelievers a humiliating punishment, and (for) those who spend their wealth only to show people, and do not believe in Allah and the Last Day. Anyone for whom Satan is companion, evil he is as a companion.” [4:36-38]

This is why one would find examples where servants or slaves were either married or freed after being purchased.
The only difference is of the rights; not conduct. And that difference too is scrupulously just in light of theism and religious conventialites.
Anyhow, the discussion at hand is not slavery.