>you can't hold the person responsible

The act of holding them responsible is supposed to determine them not do it. If stochastic behavior is impeding them in being a functional member of society then it still makes sense to remove them from society, why would you choose to live amongst people who are not behaving rationally? Or allow them to hurt other people? At the end of the day the why matters less to removing them or not from society. And sentences are clearly used as a determining factor.

The holding responsible part deals with politics and more primitive aspects of our societies and biologies. Getting tangled up in holding them responsible or not is hardly something you should give much attention to. Rather to make sure they do not cause any more harm and also make sure such things are not created in the first place. Which opens up another can of worms for which society and politicians are ready for.