I don't think I see enough posts about Eric when it comes to the Andersen Journals and just how important he is to the plot and to the characters in it.
A lot of people hate Eric for similar reasons to why they used to hate Shaun; it stems from "the truth", which is fair. We, as the audience, are introduced to a mentally ill person who's suffering and then we meet someone who point-blank calls them crazy and accuses them of malicious intention. It's ableism. That's a valid reason- but I don't think anyone stops and thinks why Eric thinks that? He's Shaun's childhood friend, Shaun's roommate, he's heard about Micheal, he's heard about what "he's" (Slenderman) done to Shaun before. It's not an excuse but it's certainly a reason, isn't it?
But he doesn't not help Micheal. He wants to help- he states that in "Eric returned", I recently transcribed it and despite everything, he's willing to help. More than that- he very evidently does not like Micheal, but he's willing to be with him. He's willing to get in a CAR with a guy he doesn't like and go to some fuckass unfamiliar place on the off chance he can see Shaun again. (The Alley). He, when he thinks Shaun is in trouble, throws himself out into the line of fire saying shit like "I thought it was me you wanted?!" [as in, to hurt, a reference to Journal 6 where Micheal says he'd hurt Eric before Shaun] (Eric/Documents).
But he's really important- and Micheal hates him additionally because he's a wall between him and Shaun ("this is a family matter" esc lines, which eric throws back at him) but because he also represents something Shaun has that Micheal doesn't, being a shoulder to lean on, someone to help and protect him.
Micheal is fucking terrified and he's going down fast and he's swinging and grabbing and digging his nails into literally anything he thinks can keep him afloat, Eric is trying to put himself between those claws and Shaun.
It was NEVER about hating Micheal, it was ALWAYS about protecting Shaun. And then Shaun is far too involved, far too wrapped up, and Eric recognizes after being put in the hospital that if he sticks around here, he's going to die. He has to leave. (In the description of "Visiting Stormy", you can see he still cares. He still tries to call Shaun, he just can't. And again, in So it goes 2, where Shaun calls him to tell him it's all safe.)
He's literally forced out of the plot. Patrick doesn't want him around, because he's in the way, he recognizes too much of what's going on, he's that wall between Shaun and Micheal. He gets rid of him. And then he tells Shaun not to contact Stormy, an effort to isolate him, and that's the importance of it. Isolated, losing your long-time best friend, roommate, and protector. Eric stood for a lot in the brother's storyline.