Comment by Taekjooschocolatebutthole on Jinx - Chapter 76

@Taekjooschocolatebutthole it justifies what he did, but that doesn't mean that what he did was right. I don't know if i explained myself. There is a reason why someone act in certain way, but that doesn't mean that you shouldn't take responsability for what you do.

@Alfjomichi  justify means to explain and validate his actions which is incorrect. There is no justifying what he's done to Kim Dan. Especially the chapter in which he has blindfolded him and made him wear headphones so he wouldn't hear Heesung come in, that's se*ual assault, as is many other instances in this story. There is never any justification for that.  

The word you're looking for is simply 'explained'. It explains why he behaves the way he does, but as OP stated, that is not an excuse for how he behaves. As you say, you have to take responsibility for what you do. He's accountable for his own actions, and his past may explain, but it can never justify.