The letter (though as you point out carceral systems probably aren't #1 contradictions) is inoffensive theoretically, and makes salient critiques. why was it published in a paper of record at the height of US aggression towards that country? what purpose, concretely, can it serve? Iran cannot reform as leftists might desire right now. So what we're left with is academics showing off how clever and relevant they are, and as consequence blunting antipathy toward the war. It's perfectly acceptable to make these critiques outside the public sphere--I'd argue this forum is enough grains out of the way we're not obliged to hold our tongues.