This is true, I did not say mirror musk was definitely good. Just that while your headcanon can be whatever you want, it really doesn't make sense in the context of the show for this to have been a slip up of someone from the mirror universe trying to blend in. From a storytelling standpoint, we as the audience have no idea who mirror elon musk was, and it wasn't treated like a strange remark, and the show does nothing to establish that the other characters see musk other than a hero or at least major historical figure that greatly impacted technology and space travel and is viewed in a generally positive light.