[xCathedra]

Expanding the definition to include animals necessarily involves redefining personhood, and that's the risk. Expanding personhood doesn't necessitate removing classes of people from personhood, but allowing for its redifitinion makes it possible.

[adamnemecek]

Your argument is similar to the argument of those who opposed gay marriage in that it claims that expanding something to another group will redefine said thing to the other group.