Why would Art call his father, a Holocaust survivor, a murderer?

Art calls his father a murderer when he finds out that Vladek burned his mother's diaries. He wished to include his mother's voice in the novel, and the only way he could have accomplished that was to use her own words.... her memories. When he finds out the diaries no longer exist, Art realizes that he's lost the one connection through which he could have come to know her..... to know about her experiences. Anja's voice had been silenced, and his father had destroyed the voice he sought. Thus, in Artie's eyes, his father had murdered her.