Yes, the foreign ownership of US ports is acceptable, because it gives those other countries that have an ownership interest in the United States an interest in keeping the United States safe. These countries or foreign business owners will have to comply with procedures for intake of goods, as well as people who come to this country. They can manage, despite not being American.
Foreign ownership of U.S. ports is acceptable so long as proper security measures are taken. Nearly anything can be a security risk if precautions aren't taken, and there are certainly many other ways that ports could be a security risk anyway regardless of their ownership. It is only that caution has to be taken.