They covered the airspace thing early in the broadcast and you're correct, there are no restrictions, so people can fly over it if they want. And they want, apparently.The Masters is owned by the tyrants who run Augusta National, not the PGA or USGA. So they have free reign to eject anyone who does not act with what they feel is appropriate decorum. (Note: unsure why the USGA or PGA does not follow their lead for their tournaments.)
The plane thing is about air traffic control. My guess is that a course in rural Wisconsin has no restrictions on the airspace, so nothing that Fox can do about it.