There's a significant qualitative difference between someone being self-destructive (albeit with traumatic consequences for those who are connected to them) and engineering the destruction of someone else.
There may be mental failings involved which are outside the control of the individual, but I don't think that's the whole story or we'd have to throw the idea of moral agency out the window (I picked the example I did because the person neither appeared nor claimed to suffer cognitive impairment AFAIK). We are actors as well as being acted upon by our environment and biology; insofar as our activities impact others, we have some responsibility to regulate them.
There may be mental failings involved which are outside the control of the individual, but I don't think that's the whole story or we'd have to throw the idea of moral agency out the window (I picked the example I did because the person neither appeared nor claimed to suffer cognitive impairment AFAIK). We are actors as well as being acted upon by our environment and biology; insofar as our activities impact others, we have some responsibility to regulate them.