This is legally incorrect. It's a meme that should die. This idea is based on the assumption that not acting to maximize shareholder value is defrauding investors. But this isn't at all true. Corporations are free to do whatever they want, as long as they're transparent about doing so.

Or to make the same point in the opposite direction: companies must act ethically, because not doing so ends up being securities fraud[0]. Since stock price is in a large part based on perception, things that negatively affect perception that aren't disclosed could be (and are) construed as defrauding investors.

[0]: https://www.bloomberg.com/opinion/articles/2019-06-26/everyt...