There is something wrong with the narrative on this. If it is truly as barbaric and causes unremitting lifelong pain, why would veterinarians do it? The position of the AVMA is educate patients and push alternatives, but not "don't do it". Why would there be so many cats who, having undergone the procedure, live 10-15 years as happy and affectionate pets? Yeah, I get that cats can hide pain. But not long term. I've had them all my life until a month ago. 

If it were as terrible as some opponents say, it seems that euthanasia would be recommended if the only way to keep the cat is declawing. But it is considered to be preferable to euthanising a problem cat who won't stop scratching inappropriately. 

I have to wonder if there are some vets that do it better than others? Studies apparently do not support a connection between declawing and bad behavior. I think there is a lot of misinformation in the arguments.