If you had actually ASKED the Sioux of the Black Hills about this, you’d know they’ve told pretty much everyone “yeah we don’t like Mt Rushmore, we don’t like Crazy Horse’s relief carving either, but we think destroying them is more disrespectful than just leaving them to fall apart on their own.” Like, this isn’t an uncommon thought. It’s just more complex than “blow them up”.
Arguably he’s done that one over and over in his speeches, and with the Central Park Five, and with the other people I’m sure he’s fantasized about killing over the years.