That's a very Brent Spiner thing to say, doesn't mean he actually hated that cat. And it wasn't just one cat playing the role anyway. Most if not all of them were good cats I'm sure.
I vaguely remember reading an interview about this though, Brent was saying the cats were terrible for not staying where they needed to be and their scenes always took ages. I don't think he hated the animals, but the resentment was real.
If I spent 7 years playing my character as a boy, only to suddenly become female for the sake of a single episode where I get pregnant I'd be pissed too.