Guy just spent 3 years of his life being absolutely hated by everyone, living a hell of a life, had to lie on his identity to get a glimpse of a normal life again, has probably the most fucked up thoughts all the time because of the whole story, can probably trust no one because close to everyone probably rejected him and treated him like utter shit after the news came out (as we can see when his "new" friends learn what he supposedly did), and people in the comment expect him to be lucid and tell everything to his mom.
Not saying he is right or the mother is wrong for treating him like this, but this is a big gray area and even if some of the stuff makes absolutely 0 sense (the face of the boy is plastered everywhere and everyone seems to know him but the son of the dude who got killed dated his sister like he was a total random person yes yes), but that is not one of the thing that makes 0 sense and it's actually in line with how he's been acting throughout the story. He went too far now to stop protecting her.