It angers him whenever he sees slaves --- not only because of how unfair it is for slaves to still exist in the Reoublic, but because it triggers his own past. He hates it.

So, as Obi-Wan takes care of the important part of the mission in the Hutt palace, Anakin crouches by your side and assesses your handcuffed wrists, in the cells.

"I'm gonna get you out, don't worry." Anakin tells you calmly, watching the chains paralyzing your body, keeping you in place and ensuring you won't escape.