I'm kind of surprised that this is even a question. Declawing is unequivocally unethical. It is banned in most countries, other than the US (where some people care more about the condition of their couch than the physcial and emotional health of their animal dependents).
Declawing a cat is analagous to chopping off the fingers of a human up to the first knuckle. I can't imagine waking up from surgery and finding all my fingers mutilated. Many cats become aggressive and bite-y after declawing, which is not exactly surprising. It can also cause lameness, arthritis, and other long term complications.
I think that declawing has become common practice in the US, because it is a convenient way of ignoring the underlying issues in the relationship between human and cat. Rather than seeing scratched furniture as a sign that a cat is missing something that it needs, people get angry, as if the cat had a vendetta against the couch. Instead of giving the cat things that it likes to scratch, many people try to punish a cat so that it 'behaves better,' when it is simply trying to fulfill its needs.
Honestly, I find the practice of declawing abhorrent and unequivocally wrong. If you don't want a whole cat, don't have a cat.
