> In the case of genuine errors, is there anybody actually arguing on the other side?
Oh yeah, that happens if your edit goes against one of Wikipedia's sacred policies (they all are). I have that issue on the Dutch Wikipedia where a number of places in the bilingual province of Frisia shifted their official names to the Frisian variants instead of the Dutch, and where in one case in the course of three decades the old Dutch name dropped out of use completely¹ except for… Wikipedia, which relies on a single outdated (or misinterpreted) document published by the national language society. That Wikipedia branch has a policy which mandates the use of that document, so even though it is demonstrably showing an obsolete name, Wikipedia editors who like that status quo (often due to a dislike of regional languages and identity — this will be familiar to Welsh and Catalan folk too) will defend those 'facts' and slap anyone suggesting change with that policy document.
To my estimate changing a standing Wikipedia policy requires being a high-profile editor for at least a decade and investing around twenty hours a week for about half a year to garner enough support to change it. Most people just consider the Dutch Wikipedia a lost cause in this regard and give up. What's annoying is that Wikipedia is often taken as authoritative in terms of simple facts (like in the case of this flag), and factual errors leak out across the internet.
1: That is, you won't find the old names in the place itself, nor used (in Dutch, or any language) by the local residents, nor on its signage, nor on its municipal website, nor in the local media (or even national media mostly), nor on most maps, et cetera.