You want a jury with good judgment. Maybe people indifferent to the publicly known actions of the accused are that way precisely because they lack good judgment. Yes, they need to judge the case in question, not everything the accused has ever done, but perhaps indifference to those facts extraneous to the case indicates they will judge pertinent facts in a way the public at large wouldn't recognize as just.
Maybe next time try not to be such a dick to everyone at all times.
Most of the world does without juries. In the US we don't use juries for all trials. The Supreme Court and circuit courts do without juries. If we don't use juries for our most important legal decisions, why are they better in the cases in which they are used?
I'm not a legal scholar. I'm sure untold volumes have been written about this. Just on its surface, though, it looks like nothing more than an accidental quirk we inherited from the English legal system.