Oh God...
Look, I'm not going to apologize for having an opinion about Loki. And yes, I'm a Loki fan and since he's a character in Thor Ragnarok I believe I'm allowed to express my opinion on him and other characters of the movie. Especially in the spoilers thread.
I'm sorry you had a bad experience with other fans, but that doesn't mean you it's alright to make other fans feel unwelcome in the thread because we also want to talk about our favorite character. No one is preventing anyone to talk about Thor, Hulk, Valkyrie or any of the other characters. There's enough room on the internet for all of us. We're all nerds here.
As for the Grandmaster scene, I don't think it means anything. It was just an awkward moment when he said that he would be millions of years old on another planet, not realizing the same happens in Sakaar.