for--seriously. This can not be decided based on emotion alone.
There are so many complexities to a ruling that makes pets non-property. Not the least are legal liabilities to those who do not pursue what a court or other considers "adequate" and "appropriate" veterinary care--even if that care includes that which are truly not feasible economically. While few veterinarians will euthanize a healthy (or treatable) animal for economic reasons alone, there is potential for the individual demanding that be done to be accountable. Veterinary care, like that on the human side is increasing dramatically in recent decades, but it may be difficult for less costly conservative care (a "wait and see" initial approach) to be offered--even where a veterinarian is agreeable.
Then there are the legal issues associated with the human component--i.e., divorce, moving, homelessness. Who gets to decide custody (and mind you, don't forget the $$ of court intervention in that respect)... As with child custody, what happens when two formerly united "pet parents" don't agree on a planned veterinary medical intervention...
This is a start. Boulder moved in this direction a number of years back but ultimately thought long and hard about some of the many issues I bring up and abandoned it.
Like many, my pup is my furry child and I'd do nearly anything for her as I have tried to do with my previous pets. But while I would likewise want society to do just about anything to prevent animal abuse -- from pets to wildlife and to the degree humanly possible, livestock, declaring pets or all animals as non-property and thus eligible for an array of rights perhaps similar to children carries with it some complications few have considered.