Do you think that someone who cares for his family would shoot them in cold blood, fight with his father and bludgeon him, etc, just to get money?
You see, I think that those who think Jeremy is guilty have to come up with another explanation - ie, that he hated his family and he hated farming.
I think it's a chicken and egg situation.
I think people who believe JB to have committed mass murder, likely believe that JB had not particularly love for the lives which he ended. Whether that manifested itself in the form of hatred, or as suggested by Caroline that he simply didn't care for them either way, I do not know.
I think it's quite reasonable for people to think that a premeditated murderer didn't care for his victims.
I don't believe hatred was the motive, but if present, it didn't act as a voice of reason.