It is correct that no shipping movements are permitted whilst an air display is in progress over the harbour. This may or may not be related to the accident which befell one of the Red Arrows during a display at Brighton in 1980 when it clipped the mast of a yacht and crashed into the sea between the piers.
http://www.mybrightonandhove.org.uk/page_id__6360.aspx
Suspending port operations for half an hour on one of the busiest weekends of the year would have been an immense inconvenience to the travelling public and would have caused a backlog of traffic to build up on the roads into the port. Since these were already jampacked with cars attending the Bleriot events, it would appear a recipe for gridlock with neither the ferry traffic nor the event goers getting to where they wanted to be.
I hold no remit whatsoever for the harbour board bearing in mind their disgraceful treatment of their workforce and their oft-refuted plans to sell off the port but the above would appear to be sound reasons for not suspending the operations of the busiest ferry port in Western Europe to enable an air display.
If so, it is to DHB's discredit that they have not managed to communicate these reasons to the population of Dover but I would charitably attribute this to a general lack of awareness and professionalism amongst the placemen currently appointed to the board rather than to an intentionally dismissive attitude to the locals. I could be wrong.
The other point I would like to pick up on is that of funding said air display. Why is it considered that the harbour board should be funding an air display commemorating the first powered aircraft to fly across the channel? They are running a seaport not an airport. Would it not be more appropriate to enquire why aeronautical bodies have not funded a display, or DDC as representative of the local community?