Anakin Skywalker hated slavery. He hated it when he'd been a slave himself on Tatooine; he hated it when he became a Jedi and no longer allowed to hate. He hated it during the Clone Wars, the Zygeria mission stirring up past memories and hatred.

As a child, he had dreamed of freeing all the slaves on Tatooine. He dreamed of becoming a Jedi, and coming back to free his mother and all his friends. The first one he did; the second one no longer possible when the first came true.

As a Jedi, he wished that there was something he could do, to help his mother and all the other slaves. But he knew his duty was to the Republic, and so he remained silent.

And then... then he became a Sith. He became Second in Command of an Empire. He could do anything now, couldn't he? He could free all the slaves now. But Anakin—no, not Anakin, Vader now—didn't think of that. Anakin wanted to free the slaves. But Anakin was dead now. Darth Vader had killed him. And Vader didn't think twice about slavery, not anymore.

Vader—or had it been Anakin? Was it during the transition period?—had once said, that he would bring peace, justice, freedom, and security to his new Empire. He had said that he was powerful enough to defeat the Emperor. But then Obi-Wan Kenobi cut off all his remaining limbs and left him to burn in the fires of Mustafar, and Vader didn't think he was powerful enough to defeat the Emperor anymore.

He needed another to help him.

And one day, he found that other, a boy named Galen Marek. This boy, he was powerful in the Force; yes, he would do well. He could help him defeat the Emperor.

So Vader took him in, and he trained him in the ways of the Sith. He cared nothing about the boy. He was just another tool to use, to manipulate, to serve his will and be discarded when finished. And if he wasn't good enough in the end, well, he'll make some clones and they'll serve him better.

Starkiller was just another slave for him, like so many others in the Empire, this new Empire that didn't change anything; this Empire that encouraged and made good use of slavery. This Empire that was built on the back of slaves.

Hadn't Vader once been a slave, too?

Hadn't he once been a slave on Tatooine, with a master that would punish him when he did wrong, and sometimes when he didn't? A transmitter chip inside him, that would blow him up if he ventured too far?

No. Anakin had been a slave. Darth Vader is just another slaver in the Empire.

And every slaver is a slave themself.