impugn vs justify

impugn

verb
  • To verbally assault, especially to argue against an opinion, motive, or action; to question the truth or validity of. 

justify

verb
  • To give reasons for one’s actions; to make an argument to prove that one is in the right. 

  • To absolve, and declare to be free of blame or sin. 

  • To be a good, acceptable reason for; warrant. 

  • To qualify (oneself) as a surety by taking oath to the ownership of sufficient property. 

  • To arrange (text) on a page or a computer screen such that the left and right ends of all lines within paragraphs are aligned. 

  • To provide an acceptable explanation for. 

  • To prove; to ratify; to confirm. 

  • To show (a person) to have had a sufficient legal reason for an act that has been made the subject of a charge or accusation. 

How often have the words impugn and justify occurred in a corpus of books? (source: Google Ngram Viewer )