Can anyone explain the senseless animosity between Avalon and St

Seaville - Can anyone explain the senseless animosity between Avalon and Stone Harbor? It's the same island! I hear people from Avalon complain about SH. Conversely, SH people mock Avalon. Is there some basis or history for this silly "sibling rivalry?" I can understand the Wildwoods rivalry, but I never hear this kind of nonsense from Sea Isle and Strathmere.