Finally, someone actually addressing the legal question in r/law
It's defined in 18 USC 2331(5):
> (5) the term "domestic terrorism" means activities that-
> (A) involve acts dangerous to human life that are a violation of the criminal laws of the United States or of any State;
> (B) appear to be intended-
> (i) to intimidate or coerce a civilian population;
> (ii) to influence the policy of a government by intimidation or coercion; or
> (iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and
> (C) occur primarily within the territorial jurisdiction of the United States;
Whether this constitutes terrorism then depends on what status Elon Musk has.
Let's say for the sake of argument that these acts are dangerous to human life (although obviously spray painting a swastika on a dealership isn't). If he is just a private citizen, then he clearly doesn't qualify as "a civilian population". He's just one person. And if he is a private citizen, then intimidating him cannot be expect to impact the policy of a government.
On the other hand, if he is an officer of the United States, then it's possible those acts would satisfy this definition.
But then of course he would need to be confirmed by the senate.
Trump wants it both ways as usual. Or to put it another way:
> Conservatism consists of exactly one proposition, to wit: There must be in-groups whom the law protects but does not bind, alongside out-groups whom the law binds but does not protect.