AFAIK, RI was never a "slave state" or "slave colony", though when it was legally forbidden I do not know.
That said, in the context of the 17th century, "Plantation" referred to a colony or pioneering settlement, not a large-scale farm dependent on slavery. See, for example the book Of Plimoth Plantation, William Bradford's book about the early history of Plymouth Colony (which at the time was separate from the Massachusetts Bay Colony).
Not that facts matter to modern Proggies.
