You want avoid a negative review even if you bend over backwards
Ans why would you? highly doubt the neighbours are ‘killing pigs all over the property’ that’s not how pigs are killed in most Western countries .
You must know what you can see from the listings - is there anything that could cause concern?
Speak to the neighbouring farmer - it sounds to put it kindly they are exaggerating.
you can then respond and say you are sorry they didn’t note the listing was between two farms, and that given they are vegetarian that they didn’t check what sort of farming takes place to ensure animals weren’t farmed.
Tell them from your knowledge of the property what can be seen in terms of the farm - and confirm this with the farmer.
Armed with information, say that although no killing of animals can be seen, from the listing- if they don’t want to continue with their stay, as a gesture of good will, if you reset any of the days you will let them have a proportional refund @Matt771