If Hacker News is about the tech industry then we need to see the tech industry clearly, warts and all.
We cannot run away from it. We cannot memory hole it.
HN isn't "about the tech industry" per se - its mandate is to discuss topics of intellectual curiosity. See https://news.ycombinator.com/newsguidelines.html. Celebrity troll moves (or whatever this is) don't fit that bill, so in this case I'm inclined to agree with the users who flagged the story.
In terms of ethics, if the intention is to generate outrage in order to generate views and media coverage, does media coverage help or harm? Research on violence has has reached a fairly strong consensus that symbolism and displaying of cultural values is a major contributor for continued violence and conflicts. What should be the most effective (and ethical) strategy in reducing such display?
Watch this at 00:35. Debunks your entire point about "the look" with Hitler doing the salute exactly as Musk did it.
I'm from Switzerland / Swiss German and maybe we just watched way more WW2 docs in high school and had more exposure to the various ways a Nazi salute can be done, but across the German speaking sphere we all saw this as a Nazi salute. In this variation it was often done with hand on breast during "Sieg!" and then the extension with "Heil!".