kick a dog when it's down vs kick someone when they are down

kick a dog when it's down

verb
  • To make things worse for someone in an adverse situation. 

kick someone when they are down

verb
  • To make things worse for someone who is going through a difficult time. 

How often have the words kick a dog when it's down and kick someone when they are down occurred in a corpus of books? (source: Google Ngram Viewer )