What you wrote above is not the experience for 99% of Imperial Slaves in the Empire. There are laws that protect slaves against exactly the kind of behavior your describing above. A slave doing a job is paid, at minimum, 80% of what a free Imperial citizen would, only their pay goes to their owner until their contract is fulfilled. Also by law, their owner is required to meet a certain standard of health care, housing, and nutrition. And by law, this standard is at the owner's expense, and is not to be counted against the slave's contracted debt. Many slave owners feel that honor requires that they exceed the minimum standards required by law, and for most they are a status symbol, a way of flaunting their wealth while helping their fellow Imperial citizens down on their luck.
When slavery is done according to law, it is an honorable and safe to way to get out of debt, to escape a bad situation, or even to better their position in life. It is better than the Federation's practice of shafting the people you owe money to by declaring bankruptcy, or living off the public dole. And studies have shown that an Imperial Slave enjoys a better standard of living, and has a longer life span, than a supposedly free citizen in the Federation, unable to get ahead due to corporate practices and the high levels of taxation in the Federation.
The reason why slavery is a contentious issue in the Empire is that some slave owners abuse the system. Dishonorable slave owners fail to meet the bare minimum the law requires, attempting to squeeze a profit off their labor. Imperial Slaves are sometimes abducted by their owners and taken outside the Empire and its protections, where slavery isn't regulated. Sometimes they're abducted and then "freed" far from home, and lack the money or connections to survive, let alone return to their family and friends. And most people who sell themselves into slavery don't have the luxury of researching who they sell themselves to, and choosing those who treat their slaves well. For most, they go into the general market, with no guarantee that some day they'll be forced into a stasis chamber, and take away by someone who feels that all slaves are the same.