Because sadly the UK is still a racist country no matter how the government try to deny it, the fact we still have separate 'ethnic' sections in the supermarkets just goes to show it :(
I personally don't like tripe or chitterlins, but my local supermarket carries both of them for folks who enjoy them. Not quite sure how that would be racist, unless certain groups are completely separated from the general population, and only allowed to shop in the ethnic sections.
Anyway, getting back to what you should or shouldn't put on your horse. Furniture polish contains toxins that can be absorbed through the skin, so I'd be very careful about using it. You might want to consider looking at the ingredients and reading the warning label before you decide to spray it on your animal.