Is 'can't remember' a reasonable excuse?

My da has been thrashing me for years, ever since I was an infant, and this and the previous year I've stood up against it and asked him why he does such things. he looked absolutely stricken surprised and blank, then told me that he didn't remember doing anything to me. I know that when his switch flicks and he's gone into bucking-bronco/bull mode he's a different guy that's pure aggressive and violent. never hit my mother or anyone else (as far as I know), just takes it out on me because I'm always the kid who stays standing throughout. Yeah sure I'm standing and not wailing like a baby or my other sibs, but on the inside I'm a wreck. I been cutting myself for a few years and quit recently with a ton of lone willpower; he's pissed at seeing me bite my lip, it's indescribable how whacko he gets when he sees scars or scabs on my arms and/or legs. Is this 'I can't remember' bullsh** acceptable? Could he really just not recall his insane rages? I know he was beat up real bad when he was a kid and so was his ma but.... really?