[smeej]

I think an "it" can have rights. I'll go back to the horse. It has a basic natural right not to be beaten because it's a creature that can experience pain, not because it's an "I."

The legal system (at least in the U.S.) seems to need to call something a "person" in order for it to have rights (e.g., corporations), but I don't think the legal system is the origin of rights.

"I" and "thou" go together as references to personhood, so I wouldn't distinguish between the two. (And I'm mostly using "thou" here instead of "you" to show I'm referring to the concept rather than you personally. The "I/Thou" philosophical concept also has precedent of using the term.)