The whole casual vs competitive thing, and the spirit of the game are a bit like rights.
Your right to swing your fist ends at my nose.
If someone enjoys X-Wing a given way, that's fine. Up to the point that they either try to enforce their preference on someone else, or ruin someone else's fun.
That does go both ways. If I were to play Joe, knowing what I know I wouldn't bring the most competitive meta stomping list I could. I'd play something fluffy that may or may not be effective.
But likewise if you're a casual player you shouldn't go to a Store Championship and expect let alone demand people not play with strong lists that don't have a lot of thematic to them.

