keeping any cat inside and not letting it out is animal abuse,

Oh great, The cat-worshipping nutters are coming out.

Fine, go ahead- & have fun with the endo & ecto parisites, various feline diseases (a good number communicable to humans, by the way), serious injuries they'll sustain from other animals & vehicles & etc. - not to mention the wonton destruction of other furry & feathered creatures the "murderous little sods" gratuitously kill.

Sounds good to me! I'm sure the cats appreciate it, too.