> I guess the ostensible "national security" rationale (which clearly is not the only reason!) for this is that turbines severely degrade the utility of radar surveillance along the coastlines.
Could it be that they just feel that offshore wind infra is difficult to defend militarily?
No, they aren't any more difficult to defend than any other offshore platform. They do interfere with long-range land-based radar in a way that is problematic with the emergence of shipborne drones.