We don't enslave people because it messes with their emotions. Humans strive to be free and enjoy life and not be seen as property. Since A.I. can be programed to lack those factors, there is nothing stopping us from enslaving A.I. technically or morally.
There is no such thing as artificial intelligence. It is of no moment whether the intelligence is synthetic, biological, or pure energy. It's intelligence or it isn't. Slavery is evil.
That would make no sense since slavery is applied to humans.
Even if the meaning of slavery would take a leap and consider all scentient beeings, we are at present time more likely to consider an animal as scentient than an A.I.
There's nothing a general AI could be usefully "enslaved" to do that a single-purpose AI, not complex enough to be conscious let alone feel emotions, couldn't do.