Honestly, and I hate to play the contrarian in the room, but MatPat's not much of a lolcow. He makes videos on theories, part of the fun of theories is debunking or discussing them and MatPat does absolutely nothing to prevent either and encourages his audience to think about vidya more than they typically would. (Whether or not that's a good thing is up to interpretation.)
The worst of his theories are just bad theories. He's not doing anything lulzy, he's not acting like a spaz, his videos don't devolve into madness or say anything outlandishly crazy or offensive, and I think it's unnecessary to even have him on here. Being a sellout shouldn't be a qualifier for a lolcow, it does nothing but influence the content to go in a direction emphasizing views which isn't even a bad thing at all. (EDIT: Inherently bad. It's a neutral stance that can go either way, don't misunderstand.)
If you don't like the content, more power to you, he gets under my skin as well, but giving Undertale to the Pope is about the most outlandish thing he's done, and with context behind it, it's not even that outlandish. (It's stupid and somewhat cringey, but it's not the worst thing he could have done.)
As for Mat himself, while I've only taken a passing glance at his livestreams, he's a lot more casual there and he doesn't take himself all that seriously. Even the FNAF thing I find it hard to harp on him, as it seems to me the developer for FNAF was having fun taking everyone for a ride, and I don't doubt the possibility of him talking with people like MatPat and Markiplier to put on a show.
tl;dr At his worst, MatPat makes some extremely hit more miss (Mostly miss) episodes of a show that I think way too many people take seriously. (The reaction to the Pheonix Wright episode is cringe in and of itself.) I don't think this thread is warranted at all. If we dedicated a page to every single person we didn't like, this website would be loaded with bullshit threads. Just my thoughts.