The only arguments against Puerto Rican statehood I've heard that aren't just bigotry:
- If Puerto Rico becomes a state they can't compete in the Miss Universe pageant anymore, which is surprisingly kind of a big deal because they've won it five times (making them the nation with the third-most Miss Universes) and won it twice last decade.
- Puerto Rico has a much lower average income than the contiguous US, so welfare programs would have to cover a lot more people, maybe causing budget issues or something.
And, that's it.
Yeah, but there is a great deal of tax exemptions, both corporate and personal, that attach to PR residency. IIRC a large number of pharmecutical companies have factories there for this reason. I don't know if shutting those loopholes will wholly offset the increased social services cost (does the federal government not largely provide such services to PR already?), but it may not be nearly such a financial obligation as some might fear.