Saying “It looks like your argument would also justify Terrible Thing X” is not (necessarily) strawmanning.
If people had the option to sell themselves into slavery, then some would take it, just as if people had the option to sell their kidneys, then some would take it.
So far as I can see, there is nothing in the OP that says “this business about taking away people’s least bad options only applies when that option isn’t too bad” or that gives any concrete reason why “don’t take away the option of selling yourself into slavery” would be wrong while “don’t take away the option of selling a kidney” is right.
Saying “It looks like your argument would also justify Terrible Thing X” is not (necessarily) strawmanning.
If people had the option to sell themselves into slavery, then some would take it, just as if people had the option to sell their kidneys, then some would take it.
So far as I can see, there is nothing in the OP that says “this business about taking away people’s least bad options only applies when that option isn’t too bad” or that gives any concrete reason why “don’t take away the option of selling yourself into slavery” would be wrong while “don’t take away the option of selling a kidney” is right.