The American Meat Science Association defines meat as red meat (beef, pork, and lamb), poultry, fish/seafood, and meat from other managed species (AMSA, 2017).
Fish, by definition, is meat.
Other simpler definitions around the world sinply say "flesh of an animal". At that point, you're arguing that fish isn't an animal.
I have no problem believing that every society has ludicrous cultural vestiges that can undoubtedly be traced back to a religious practice. For example, some Pope might declare that fish isn't meat based on an example of linguistic sophistry to protect the fishing industry.