No one ever kicks a dead dog
Look at the Palin hate in the comments. - Anna Puma
I was going to post this a few days ago regarding Cruz-hating, but it's just the same:
"The day he was inaugurated, a friend said to the father of Robert Maynard Hutchins: 'I was shocked this morning to read that newspaper editorial denouncing your son.'
"'Yes,' the elder Hitchens replied, 'it was severe, but remember that no one ever kicks a dead dog.'"
From the chapter "Remember That No One Ever Kicks a Dead Dog," in How to Stop Worrying and Start Living by Dale Carnegie.