Biology, Brain tumours and mental disorders, behaviour and Budhism
Buddhist practice doesn't start from the premise that the world is a just and fair place; rather, it aims to reveal that all conditioned existence is marked by suffering.  Suffering is the real problem and assigning blame doesn't help to alleviate it.  It's also not particularly helpful to consider what-if scenarios like "would I still be to blame if I had a tumor and couldn't control my actions?"  I have enough real problems without imagining new ones

See, reality doesn't happen to someone else and it doesn't happen somewhere else or at some other time.  Reality happens right here, right now.  This is not a hypothetical practice, this is a real practice and it deals with a real problem, the suffering that marks every passing moment, the clinging that creates it and the out-of-control mind that is churning away with these thoughts.  Not, "who's to blame for that?", but "who's to blame for this?"  Maybe drop the blame and just look for the cause.  Maybe drop the cause, too.  Just look.

Ultimately, Buddhist practice urges us to investigate this matter thoroughly, to find the root of suffering.  And then, remove it.  Perhaps this whole sordid affair is predicated on a misunderstanding, a subtle delusion that got out of control.  The Buddha suggests that there is such a cause to suffering and that it is possible to remove it.  The path of practice is prescribed as a way to purify this mind and reveal, with full clarity, the reality of this situation.