How we cite our quotes: (chapter.paragraph)
Quote #4
"You've got to stand up to him, Neville!" said Ron. "He's used to walking all over people, but that's no reason to lie down in front of him and make it easier."
"There's no need to tell me I'm not brave enough to be in Gryffindor, Malfoy's already done that," Neville choked out. (13.28-29)
Ron's trying to encourage Neville, but Neville takes it as an insult. It's too bad, because Ron's right – they all have to "stand up" for themselves. Yet, that's easier said than done, especially for someone like Neville, who's frequently made fun of and shamed by the idea that he's "not brave enough."
Quote #5
"It's people they feel sorry for. See, there's Potter, who's got no parents, then there's the Weasleys, who've got no money – you should be on the team, Longbottom, you've got no brains."
Neville went bright red but turned in his seat to face Malfoy.
"I'm worth twelve of you, Malfoy," he stammered. (13.77-79)
Malfoy just doesn't stop with the insults, does he? We're guessing that, in this case, he's being so cruel because he's jealous: the Gryffindor Quidditch team is actually very good, and they really have assigned the best players to the field. Since their team is a match for Slytherin technique-wise, Malfoy tries to undercut them on a morale level. It takes a lot for Neville to reply to Malfoy here, even if it doesn't accomplish very much.
Quote #6
Harry caught Neville's eye and tried to tell him without words that this wasn't true, because Neville was looking stunned and hurt. Poor, blundering Neville – Harry knew what it must have cost him to try and find them in the dark, to warn them. (15.9)
Harry's right to feel sorry for Neville here; Neville's sacrificed himself on Harry and Hermione's account, and Harry can't even tell Neville the truth about what went down. So often when Neville tries to be brave, he gets in trouble himself: here, he gets detention.