I would guess that if you would think it is wrong to eat animals, then no one is going to breed those animals in a large scale. You don’t really need to enslave the home erectus. Anyway if they are not really all that smart, exactly what role are they going to play? We don’t enslave people with low IQ. If they cannot take care of themselves; we have people care for them, or at least intent on that. Other higher primates we don’t enslave. I assume we would do like we do those. We preserve in the wild, and we preserve some in a zoological setting. Granted we use some in research; it’s a controversial topic. I assume there would be further debates about that.
In conclusion, if they were not extinct, there numbers would never be that huge. Given the huge amount of land they would need in the wild, perserved land would keep their numbers low. In a domestic situation, I doubt they would be practical to have as slaves, making the point rather moot. As a food source, granted we are still debating objectively the rightness or wrongness, it would be another moot point, because in general I would think it would be taboo to eat them. A small modest number would be used for various research.