I'm sorry you had to experience this LadyAlizarin, and anyone else who had to D: I know the feeling of getting attacked for now reason x.x But I'm going to try and explain the Warrior RP's point of view, since I used to RP as Warrior cats and I have read the series. So here I go (just to be clear Im not defending or attacking any side, just simply trying to shed some light on the other side of this problem)
In the series, the main enemy of the Clans were other Clans. But, of course, it would get a bit boring if all the cats did was beat the stuffing out of each other. So, the Erins had to add more antagonists. They chose Dogs, natural enemies with cats. Makes sense right? But in the fifth book in the first Arc, the main Clan had a huge problem with a pack of dog-wolf things, and they defeated them. So that takes dogs out of the picture for a while. So again, an antagonist spot is needing to be filled. So foxes were chosen. The the books (obviously not in real life as shown above) foxes cannot communicate with cats, and would attack without question, and would sometimes be mentioned at Gatherings (when the Clans join together) when they ate a kit. So I am guessing the Warrior RPs are trying to stick to the books as much as they can, and so when they see a fox, the connect the dots.
Then again though, it does not give them the right to attack random RPers out of no where. So yeah, just trying to give the other side of the situation x3x