It's historically true that civilized societies--the ones that treat people with greater equality--develop technology faster, and that slavery is more a hindrence than a help in developing an advanced, technology driven economy.

However, I don't believe that technology, in and of itseslf, makes us better or more empathetic towards our fellow humans. Many repressive regimes are willing to use whatever technology they can get their hands on to bolster their power, and many people in the world do not view all other humans as equals.

I am working on a sci-fi story set in an alternate world where an autocratic empire is the major world power, and it only really requires a little suspension of disbelief for slavery to exist in it.

As I read history, I've come to believe that we are not born with the idea that "all men are created equal;" it's something that has to be ingrained in us as we grow up. Otherwise, how could the most "civilized" peoples take slavery for granted for most of human history? Technology itself does not change that mindset.