Except that he does not start with that — he starts with an unequivocal apology. As someone with no skin in the game and who doesn't know these people, it sounds like he's trying to explain why he didn't realize sooner that he was such a raging asshole to Matthew. (I understand that Mattias apparently has a history of this kind of behavior that this apology does not address.)
I read it as justification, which is typical in half-assed apologies. If that were the only flaw, I might call it a reasonable mistake. But given the other issues (failure to look at pattern, failure to work toward preventing similar future issues, failure to make amends), I think that's too generous a reading. To me it looks like part of a pattern.
