Readers will note the sly conceit that what matters, all that matters, is the sum being stolen this time, not the whole at knifepoint or gunpoint business – as if this lively means of cash extraction were some trivial detail, beneath acknowledgment. A thing with no informational content, no clues as to the character of the perpetrator, their fitness for a civilised world.
Those pointing to the smallness of the sum as if it were a significant mitigating factor don’t seem troubled by the implication that someone who will violate others, and threaten them with death, for a mere $20 is someone who will use very small incentives to behave in monstrous ways. Likewise, the implication that robbing people with only $20 to surrender is a matter of no import.
On three-strikes laws and the contortions of progressive critics.

remove the $20 from he offense. keep the knife. now what is the penalty? doofus. may a love one DIE for $20
Let’s assume that Brian Rosenwald, the “historian”, has extorted or robbed people at least 3 times, and thus has a self interest in ensuring that Three Strike laws are never put in place.
Automatic bail comes to mind, regardless of the prior offences.
Well, there’s a place for automatic bail, but it’s on a sinking boat, not in the justice system.