The venue has a reputation for being....shit (they booked Gavin McIness on one of his little tours a while back). Each year, someone in my city puts on a metal fest there and lots of nazi bands from Europe come over and play, and apparently openly fascist shit is sold at the merch booths.
Last year I emailed the local city council about it. They were useless. Right now, I'm about to email the music section of my local big paper about it, AND OFFER RECIEPTS (since I can easily compile a good amount of evidence of nazism) to see if they wanna shed some light on it.
What else can I do short of 
?
Please don't let this be dark lord day please don't let this be dark lord day
It is not. All good.
Phew. Anyway I think the best way is what you're doing, definitely let the media know. It's unfortunate but that's probably the best way to put public pressure on these assholes. Or it'll end up being free publicity for Nazi Metal Fest and just make it more popular. Hopefully not though, metal fans are usually pretty anti Nazi.
I think I CC'd everyone in the music section on my email. Now we wait for a reply.