Defense lawyer quits because of "the horrific way this boy was killed."

Gerard Marrone was a lawyer for Levi Aron, who is accused of murdering Leiby Kletzky:

"I have three little boys," he said. "You can't look at your kids and then look at yourself in the mirror, knowing that a little boy, who's close in age to my eldest son, was murdered so brutally."

What is the argument that it is ethical for a lawyer to express himself publicly like this, to the detriment of his former client?