The picture in the story doesn't fit as cruise ships are unable to dock at Nice anyway- they have to anchor off and tender ashore.
As noted the number of calls has been in decline because tendering is not popular with either cruise lines or passengers, and such calls often have to be cancelled (at any tender port) when weather conditions are too rough for tendering.
If you read the whole article this is typical Nimbyism as the Mayor is quite happy for the ships to go up the coast to Cannes (another tender port). How does he propose to stop people who land off the ships at Cannes coming to Nice on the train, bus or cruise ship excursion?
What is actually proposed is a ban on ships of over 900pax and 190 metres long. No idea what is magic about 900 passengers (as opposed to 1,000. There is no linear measurement where ships of x length can take y number passengers- that is a complex measurement.
It would also be interesting to know the size and passenger capacity of the ferries from Nice which serve various Corsican ports.
If you want to dictate how I come to your city (any city), I'm not going to come to your city at all. Especially (Nice) when you allow an airport to exist within your city with all it's low cost flights but want to dictate whether or not I arrive by cruise.