> is it justifiable
Generally speaking a lot of things can be "justifiable" with varying shades of no, but I think the word you may mean is ethical, in which case it is varying shades of no.
>cut vocal chords, declawing
>spaying and neutering
Mainly this is actually done to cut down on the number of ferals, which of course in turn leads to more animals with more sufferings getting randomly hit by cars and such or given away to "shelters" which execute most stray cats and dogs they get without ever finding them a home.
>docking tails and ears
No. Mutilating a dog's ears or tail I find especially cruel since they use them to communicate and detect things.
Most of the people who engage in these practices are already some of the worst shit human beings anyway, who often do things like that because they'd rather have their animal mutilated than bother with a potentially dirty tail wagging. I don't even know why someone like that would get a pet to begin with.