As far as I’m concerned, he can give his cat away for any reason or no reason at all with no gripe from me, as long as he found a proper home for it (which it sounds like he did). I don’t see any reflection on his character other than someone who doesn’t like what the cat was doing (and I can understand that - I don’t like cats who won’t use a litterbox reliably, either).
I wouldn’t be upset with someone for giving away a cat to a decent home, or even for having a cat put down, as Baker did, because I know every effort was made to deal with the issue, and if it’s unresolvable the options really narrow.
I love my cats, but one of them pees outside the box. I suspect the deaf cat, who is kind of weird anyway, and can’t go outside because of his handicap. It will mean eventually removing the carpet and having bare floors, which will be okay, but it’s a lot of work to look forward to, you know?
Hell, my cats barely acknowledge my presence anyway. I could give them to a serial killer and they’d be just as happy as they are here, I think. Your uncle’s cat is probably perfectly happy in it’s new home, so all is well. 