My thoughts are that the passengers are all tax-payers who fund the Coast Guard. Those are the people the coast guard are assisting, not the cruise line.
Carnival paid for its own tugs, etc etc.
It isn't as if Carnival need CG assistance every week. There are plenty of companies that operate in the US without paying federal taxes - look at all the foreign airlines.
And besides that - we HAVE a funded Coast Guard already. Isn't it their job to help people at sea in distress? It isn't as if we need to expand the Coast Guard - they would be out there anyway.