You are equivocating over the word 'responsible'. His actions were the proximate cause of his death (a meaning for the word 'responsibility' which does not imply moral judgement), but others are culpable for his death (another meaning for the word 'responsibility' which does not imply proximate cause, but does imply moral judgement). So, it is perfectly meaningful to say that people who commit suicide are primarily responsible for their own deaths in the first sense, but primarily not responsible for their deaths in the second sense.