I don't think any of us are trying to argue that Islam originated slavery, not are we trying to argue about the etomological origins of the word slave.
All of us understand that the practice is as old as human civilization itself.
We're simply stating that modern African slavery has Islamic origins.
Up until the last round of Islamic expansion was smacked down at the gates of Vienna and the battle of Lepanto in the mid 17th century, Europeans were also captured and sold into slavery by the Religion of Peace. The biographical account of one such slave, a distant cousin in my family tree, appears here.
Muslim slave raiding did not end in the 1600s. As can be seen by our own wars against Barbary in the 19th century.
The only thing that finally stopped slave raiding in the Med was European conquest of N. Africa.