You could make the argument his twitter use is distracting from the mission and I agree in part. I think it's hard to say whether it's a net negative or positive for SpaceX and Tesla, because a lot of what he posts is about those companies. It might be better if he just stuck to that.
First off, I don’t think the average twitter user is in the market for a rocket so I don’t see the point. Second, the target demographic of Tesla is not people who are all in on voting Republican, they are a lot more likely to be affluent eco conscious types, so Elon shitposting about politics is definitely not great for the brand.
