Perhaps the best way for Cork Airport to counter it is to open negotiations for better services to Cork Airport.
Currently, it's served by a bus to the city centre, the Cork-Kinsale bus, which has it as a stop and the Citylink service from Galway.
No service to West Cork. No service to Killarney. No service to Waterford (where it is significantly competing for passengers with Dublin and where there are direct buses to Dublin Airport). No service to Fermoy, Mitchelstown, Cahir, Cashel or Clonmel.
From Waterford, it takes 3h 15m by public transport to Cork Airport and 2h 50m to Dublin Airport, despite the journey being 50km shorter.
While the airport can't force bus companies to start routes, it can encourage them. Presumably, this doesn't happen because of fear of losing parking revenue. In the longer term, if it reduces passenger numbers, it reduces the viability of air-routes and money is lost anyway.