Папа Римский выпустил специальную буллу объявляющую кошку животным нечистым и подлежащим уничтожению. Христианская церковь полагала, что сатана может принимать образ черного кота, инквизиция преследовала почитателей кошек. И вообще - кошка пособница ведьмы. В костер ее вместе с хозяйкой.
Кстати, изумительный музыкальный инструмент из продвинутого христианского средневековья:
A cat piano or Katzenklavier (German) is a musical instrument described by Athanasius Kircher. It consists of a line of cats fixed in place with their tails stretched out underneath a keyboard. Nails would be placed under the keys, causing the cats to cry out in pain when a key was pressed. The cats would be arranged according to the natural tone of their voices. (http://en.wikipedia.org/wiki/Katzenklavier)
In order to raise the spirits of an Italian prince burdened by the cares of his position, a musician created for him a cat piano. The musician selected cats whose natural voices were at different pitches and arranged them in cages side by side, so that when a key on the piano was depressed, a mechanism drove a sharp spike into the appropriate cat’s tail. The result was a melody of meows that became more vigorous as the cats became more desperate. Who could not help but laugh at such music? Thus was the prince raised from his melancholy. (http://www.boingboing.net/2006/02/28/cat-piano.html)