What about Menemsha?
I doubt they’d go to Menemsha. It’s a white as the driven snow. Not enough shock value potential there.
Oak Bluffs is the most commercial and racially-diverse town on the island. There is a fairly meaningful club there that is frequented predominantly by blacks (to be fair, a few doors down and across the street on Circuit Avenue is a club that is frequented predominantly by whites). There is also Inkwell beach.
I can understand why a white supremacist group (or a false flag operation with a GAP account…) would target Oak Bluffs vs Menemsha or Edgartown or Aquinnah or Tisbury.