It’s in the main body of the Constitution. You would need a new Constitution.
And Salon is telling its readers to mob justices:
If you see them on the street, or in the post office, or in a restaurant, confront them. Tell them they don’t have your respect. Tell them they are illegitimate justices on an illegitimate court
No, one constitutional amendment could do it, however unlikely that is. There is nothing about the “main body” of the US Constitution that is impervious to the amendment process set out in that constitution.