>> some of the tech world has put in significant effort to silence conservatives
It's true, but that would be within Twitter and Meta's rights. The real issue was that they did so at the behest of the incoming administration, in behind-the-scenes meetings. It's the involvement of government officials that may have broken laws and trampled the First Amendment. Also egregious and painful to see was that they shadow-banned accounts rather than banning them outright.
But I don't see how that has anything to do with a private, non-government advocacy group making their feelings known to advertisers. It happens all the time. Conservative groups call to boycott Budweiser, liberal groups call to boycott Chik-fil-A. It's not illegal.
However, it's effective as a stunt for Elon, because saying that a Jewish advocacy group has the power to shut down his business implies, as subtext, the unspoken bit about Jews controlling the world. The statement and the choice of target leans on that implication. And the quote where he jokes that they're a defamation organization, as opposed to "anti-", reminds me of Sartre's quote which is worth repeating in full:
"Never believe that anti-Semites are completely unaware of the absurdity of their replies. They know that their remarks are frivolous, open to challenge. But they are amusing themselves, for it is their adversary who is obliged to use words responsibly, since he believes in words. The anti-Semites have the right to play. They even like to play with discourse for, by giving ridiculous reasons, they discredit the seriousness of their interlocutors. They delight in acting in bad faith, since they seek not to persuade by sound argument but to intimidate and disconcert. If you press them too closely, they will abruptly fall silent, loftily indicating by some phrase that the time for argument is past."