The only thing immature is the reaction, it's not a professional setting and he's not abusing the substance. It's purely just down to shock media reaction. Nobody mentioned the whiskey they were drinking either but that doesn't make a headline.
It's more than that. Journalists hate Elon Musk because he called them out a few months ago.
The same media outlets ranting and raving about how terrible our marijuana/drug laws are and how we need to legalize them are whining about musk smoking weed in california ( where it is legal BTW ).
It's just your routine biased hit piece by the media.
Drinking whiskey is not a federal crime. Smoking pot is.
https://www.legalmatch.com/law-library/article/federal-marij...
But it's apparently too sophisticated a point for the article, which is pure clickbait.
I'm pretty sure the federal government will do nothing about this, as the resource implications, political will, and the reaction from other business leaders who will look on skeptically at the governments actions over what has already been deemed to many as a victimless crime (with regards to the actual possession).