IMHO, judges like to make it seem like questions of 'cruel and unusual' are much harder than they really are. The reality is pretty simple: if the jury that tries a case would determine, based on their evaluations the facts including things like witness credibility, that a particular punishment would be unreasonably cruel and unusual for the actual criminal acts performed by the defendant, such a punishment would be cruel and unusual, and thus illegitimate. If a jury feels that a particular punishment would be just and appropriate, chances are, it is.
Today, the government declines to tell jurors about mandatory sentencing laws, and forbids defendants from telling them. The reason is simple: if jurors knew about such laws, they would do their duty and acquit rather than impose illegitimate punishments.
After many years of striving to reach some objective criteria for pornography, the SCOTUS finally accepted the notion of “community standards”, for it, and it alone.
Yet they just cannot reconcile that such community standards should apply in other ways, to Bill of Rights civil rights, as well as to extrapolations of those, such as a “right of privacy”, which they used to justify Roe v. Wade.
Instead, they allow the federal government to impose the perversity that it wishes to impose throughout the US, in increasingly bizarre ways, no matter how objectionable it is to the rest of the nation.