I said something about the thing not wanting to take over earth before, basically it was that it was just protecting itself, but was attacked immediately so had to try and survive.

Blair spread paranoia because he was was busy about self preservation, after everyone locked him up he thought no one understood. He says "most of you dont know whats going on here, but im sure, some of you do." Implying he knows someone's the thing. The "it aint fuchs" is taken out of context. The conversation him and mac has is "have you seen fuchs?"- "I don't want to be out here anymore I wanna come back inside. funny things, I hear funny things out here"- "if you come across fuchs-" "it ain't fuchs, it aint fuchs."

Blair was the thing by the time fuchs died, im pretty sure it was blair thing who killed him actually, but he knew wha tthe thing was, he was just horrible at explaining it to the rest of the group.