@Laura2592 How would you feel if you came to visit Berlin, and saw swastika banners hanging from my neighbors' balconies? Not that you would - that symbol is strictly illegal in Germany - but I certainly wouldn't take that as an occasion to condescend to you for being alarmed or worried for your safety as an outsider.
Perhaps it's easy to forget when it's just a normal background detail in your region, but like the Third Reich banners, the Confederate flag also represents something extreme and deeply painful. We're far past the point in time where there's any plausible deniability that one's intentions in flying it are confrontational and inextricable from white supremacist ideology. I don't think this necessitates a warning or disclaimer on your listing, especially considering that these sightings may have occurred many miles away from your cottage. But I agree with @Debra300 that you would do well to acknowledge that the guest is processing something upsetting, and might appreciate a more engaged and compassionate response. You may be their only contact in the area, so how you respond will have an outsized impact on whether they feel safe or any sense of solidarity in your community.
Circling back, I do often find myself in the awkward position of comforting visitors who find themselves taken aback by the stark reminders of the many traumas embedded in Berlin's modern history, and shocked by how persistent Nazism is just at the edge of the mainstream. I could rightfully question why they chose a destination like this of all places, but that is not 5-star hospitality. Knowing that guests have chosen my home as a refuge in a world that can be frightening, a little reassurance goes a long way.
