The cultural/political issues are deeper than you'd think, there are some within Catalonia that would claim all of us Catalan speakers as part of the same cultural umbrella, negating our own cultural background as derivative.

That's why I say that I personally (as a Mallorcan) would much prefer the language to be associated with a Spanish flag than a Catalan flag. Some people would agree and some would disagree – ultimately the best thing is to not link flags to languages anyway.

To give you another example from Issen, they're also using the American flag for English which is probably even more controversial :)