But it could be argued that states are only required to observe the Bill of Rights with respect to citizens.
Upon rereading the 14th Amendment, it appears that this incongruity is avoided by the Equal Protection Clause. While the privileges and immunities clause does only refer to "citizens," if a state (for example) inflicts a cruel and unusual punishment on a non-citizen, then it has denied to that person the equal protection of the laws.
To those who would deny all rights to non-citizens: I would say that this interpretation has no support whatsoever in the Constitution. For example, the 3rd Amendment refers to "the Owner," the 5th to any "person," the 6th to the "accused," and so forth. There is absolutely nothing whatsoever to indicate that these rights are only restricted to citizens. With all due respect, I think that this argument is but a fiction.
To those who differentiate between the "People" and "persons," I would ask, what the justification is for making this distinction? For example, in the 4th Amendment ("The right of the people to be secure in their persons..."), the use of "people" may have been just to avoid the awkward formation "The right of persons to be secure in their persons..." If there is anything in the writings of Madison or in the congressional debates that supports this distinction, then perhaps I would accept it, but as it stands, I don't see why "people" necessarily means only "citizens of the United States."