This genre of leniency pleading confuses me.
It’s basically an outright agreement(sometimes even theatrical exaggeration) with the notion that your client is a depraved character with extremely strong tendencies toward criminality and abuse of those around him.
Perhaps when comparing him with some abstract free-willed-decider that’s exculpatory; but when considering how long it would be wise to have him on the other side of a prison wall from society, whether he’s a parole candidate, what his odds of recidivism are, etc. it could hardly be more damning.
It seems like it’s just begging for a “OK, in light of the circumstances, it would be cruel to punish your client; but as you’ve so forcefully pointed out he’s a profoundly damaged menace to society, so we have no choice but to commit him to a secure ward for treatment of indefinite duration.”