Slavery and eating animals

[Esquilax]

I eat animals because I understand my own nature as an evolved organism that is an omnivore, with a physical requirement that I do so. Since morality must take into account the physical realities of the parties involved, there can be nothing immoral about eating animals because of this.

This is contrasted with slavery, where our evolved nature as socially grouped organisms is directly contradicted by the effects of slavery. The two concepts aren't so alike as the OP would like us to believe.