Supporters say the campaign doesn't mean they value the dog's life above the child's.
"This is not Kevin versus Mickey," said attorney John Schill, who is representing the dog in the court petition. "Having Mickey killed is not going to take away Kevin's pain or injuries. The only thing this is going to do is kill a poor, innocent dog."
Pit bulls are viewed by some as a dangerous breed, a reputation their fans dispute.
Guadalupe Villa, who was at the scene of the attack, filed the vicious-animal petition to have the dog put down.
"I just looked at all this as this could have been my son, and I don't want it to be someone else," Villa said.
Schill said he is working pro bono at the request of The Lexus Project, a nonprofit that collects money to legally defend canines in danger of being euthanized. The organization has set up a trust for Mickey that has received more than $5,600, he said.
Schill said the person watching Kevin while his mother was at work should be held responsible.
"But for adults involved, this never would have happened," Schill said. "They're trying to put all the blame on Mickey."
Villa, whose boyfriend's mother was baby-sitting Kevin the day of the attack, said her friend is not to blame.
"She took amazing care of that little boy," said Villa, who claims in the petition that Mickey killed her dog last year.
According to Villa, Kevin picked up a bone lying on the ground near the dog, which was kept on a chain. That's when Mickey suddenly attacked Kevin, Villa said.
Villa said she can't understand the Facebook attention and doesn't see Mickey as a victim.
Kevin was hospitalized at Maricopa Medical Center with a broken eye socket, cheek bone and lower jaw bone, according to doctors.
Dr. Salvatore Lettieri, a Mayo Clinic physician and chief of cosmetic surgery at Maricopa Medical Center, said he was able to fix the broken bones and reattach the muscles that allow Kevin to open and close his eye.
"He still can't open his eye. We'll need to fix the tear duct drainage system — that is if he makes tears," Lettieri said.