Unless this flag is not forbidden by some law (what I doubt, since I see it everywhere whenever I see footage from the USA), it is okay to allow it in cRPG. Forbidden flags (e.g. the Nazi Swastika), sexual content (which is restricted in general by an age limit) and similar stuff should not be tolerated though. So if the devs disallow this flag, due to not being medievalish enough, it's another story. But offensive? Not really...