Goes to show how much this isn't about Luigi, or even Brian Thompson. It's about the elite sending a message to the other 99%. Think, even if their case against Luigi is rocky at best, all that matters is they can get him to pay for Brian, regardless of whether he did it or not, or where the evidence points.
All that matters is that we the "peasants" get the underlying message:
- If you kill/harm an elite they'll chase you and make you pay with the full weight of their resources (and emphasis on "resources", not necessarily "law").
- If you did not kill or harm an elite you're still at risk, because then they'll choose a "peasant" scapegoat to pay anyway.
All that matters is that they get to take their pound of flesh, and that the "peasantry" gets discouraged to fight for their rights as the elite takes, and takes and takes.
Which is why it's so important that regardless of Luigi having done it or not, he should walk free unless there's solid, undeniable evidence of him doing it, like an actual and verified non-deepfake video of the assassination with his clear face on it. And even then he must only face the consequences the law demands, and what others would face in his place for killing the everyday average Joe. The fact that the life lost was an elite should have no bearing on the consequences.