Can Slavery Be A Good Thing?

Yes it can.

In fact, when slavery is beneficial, it goes by the term "taxes." Of course, all taxes are harmful in some way, but they might be the best option in certain cases, such as with the provision of public goods like defense, pollution control devices, etc. In theory, private armies and police forces might be a pretty good idea, but we don't know for sure -- as empirical evidence is lacking.

Regardless, taxes are still slavery. How so? Well, it's easier to see in a barter system. Say that your job is trading apples. And whenever you trade two apples for other items, a bully comes along and forces you (with threats of violence) to give one apple to him without getting anything in exchange. Now, the bully can eat the apple or give it to someone else, but regardless, he forced you to produce an apple and hand it over. He forced you to work for his benefit. That is slavery.

If it happens that he gives your apple to someone who is not as affluent as you, then you are a slave who is indirectly working for a less-affluent master. And yet, this bothers relatively few people. In fact, the tangible benefits of slavery are often subordinate to the high morality of this sort of slavery. Redistributing apples is considered a valuable end in itself.

Which makes on wonder: Why does anyone object to slavery?

Once again, the answer has nothing to do with "freedom" or "rights" or any similar lofty abstraction. Instead, it once again comes down to envy. Slavery is considered bad if the slave masters are more affluent than the slaves -- but slavery is considered highly moral when the slave masters are less affluent than the slaves.

To summarize: Slavery can be a good thing under some circumstances -- and there will be no objection if it feeds into envy as well. Which, among other things, explains why modern-day slavery (taxation) is as popular as it is.