Scans_Daily

Matt's anger was, at the time, focused on Fisk, and he was pretty burned out on it by the time he got to those revelations. But he specifically forgave Karen for the secret identity sellout, and while Matt is a long way from perfect, he at least stuck to that one.

He and his mom never really got a chance to address their baggage, by contrast, and if you just bottle up that kind of issue without addressing it at all, well...

What makes Matt angry here is Karen apparently refusing to take responsibility for her past, buying into the "evil baby made me do it" theory. He's sure not a saint here and that last thing he said to her will haunt him later, but the root of his frustration is a lot more understandable than it would've been if he'd gone back on his word.