They dislike him because he basically talked over everyone and was screaming the entire time. I understand it's fun to watch someone having fun, but most people were watching the stream to get information. Information, which was basically not given because of one person screaming and interrupting the other two with nothing more than "OMG THRALL, CLOSE ONE!!!". It doesn't make anyone a bad person for not liking him or being frustrated that they basically had to sit and listen to him scream for an hour in hopes of getting information. I'm sure his 13 - 16 year old fan base will disagree with me though.
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They dislike him because he's the son of Omnigol and everyone hates the Omnigol strike. Also the phrase, "Silence her screams!"