Harry knows how to make an entrance all right!

Ah, and that will not be pretty! Not at all.

Yes, and she really deserves all of it. 

Draco is now being encouraged to cause trouble by Umbridge as the head of her Inquisitorial Squad.

No, Severus isn't unbiased, but Hagrid is and Hagrid agreed that James was a bully and nasty to Severus especially.  Of course Harry would feel upset upon learning that, since he too was a victim of another bully--his cousin.  And while he is upset at James, he doesn't despise him.  He now sees him as an ordinary person--not a perfect hero.  Because, that's how he was presented to harry by DD and Sirius and Remus--they totally overlooked how he hurt another person for years and as Sev says, it wasn't just him, others were hurt too by their so called pranks.  In canon, Lily tells James that he goes around hexing people in the hallways and thinks he's all that because he plays Quidditch.  She despises him because of his arrogance and willingness to hurt another person--"because he exists".  The fact was that the Marauders were a bunch of bullies and as I said before, I hate people like that.  So, I'm going to point that out over and over.  And Harry knows that eventually James grew up, if he hadn't Lily wouldn;t have married him.  And he became a decent person, but as a teenager he was awful. 

And no, Sev wasn't perfect either, but Harry sees the remorse from him and that seeing makes it easier for him to accept Severus's failings. Remember, Sev came back after two weeks as a DE, and yet was still despised by Sirius and possibly James as well. And neither of them ever expressed remorse for what they did to him in school, so he has no reason to feel fondly towards them. Plus, all this time as Severus's familiar  has softened Harry towards the other.  He knows Severus has spent his life atoning for following the dark Path, 14 years as a spy enduring Voldemort.  But he still has some issues with him as well, for bringing te prophecy to Voldemort.

Harry, at this point, only is upset and angry with Dumbledore and rightly so.  He still counts Ron and Hermione as a friends and he still loves Sirius, but needs to discuss why he behaved the way he did at school, because that really bothers him.

I thought it would be neat for McGonagall and Sev to team up and suggest that to Trelawney and DD.  And DD defends her in canon, but doesn't seem to do much more than that afterwards.  But at least here a reason is given why that's so.  There never was one in the books and it puzzled me.

Yeah, Harry told him just what he thought, no holds barred.

He really let off some steam there! But it was bound to happen, given Sirius's current attitude.