The swastika had been around thousands of years before it came to be associated with the Nazis. Would your opinion still be the same if she had a swastika tattoo? It doesn't matter that the symbol was used by other cultures. What matters is that 95% of people out there are going to immediately think "Satanist!" something that is guaranteed to offend people. Crosses aren't going to offend anybody. What if someone comes into this shelter to adopt an animal, sees that shit, then decides to take their business elsewhere? That is money out of the owner's pocket, which seeing as this is an animal shelter and they are seemingly always in need of money, is creating a big problem. Even if it is just one or two people at the job the bullshit that it induces between them will reduce everyone's productivity. I say the best and most painless option is to suck it up and cover it up, or get started on looking for another job. Or you know just the threat of legal action is enough to get most people to capitulate. I wouldn't want to actually sue the fucker, get involved in a long drawn out court case that proves and solves nothing.