You should also post this on !washington@lemmy.ml
Not to be negative, but it will probably have limited practical effect posting about it on this community, since probably only a very small percentage of us live nearby (unless tonnes of people in this community are from Washington for some reason I'm not aware of).
That said, I suppose it's a good reminder for us all to be vigilant about these kinds of businesses, no matter where we live!
For greatest practical effect, I'd post 1-star reviews on every review platform they exist on. Just point out the facts, plainly and briefly, and there can be no reason for the review to be taken down. Plenty of people specifically check the 1-star reviews to see if there's any red flags about a place.
If you want to drag their average rating down and increase the chances of people seeing this information, ask friends and comrades to leave 1-star reviews as well, with the same guidelines (factual, plainly-stated, and brief). Probably best they don't post the exact same thing, though, or they could get taken down as spam.
You can also consider finding ways to get it into local media, not only because local people might see it that way, but also so that there's details to be found online if people go looking for information after seeing one of those reviews.
I guess you could also picket it directly, but that's a significant time investment (although even a couple of weekends might make a difference, especially if the information then spreads by word-of-mouth), and some people might not be comfortable exposing themselves to potentially being identified and targeted.
Am I forgetting anything? I'd be interested to hear anyone's ideas for action on this kind of thing.