You have the legal right (and in some states, a legal obligation) to run away from a threat.
Arbery was chased through the street and tried to get away from his attackers. If he had shot them after they clearly menaced his safety, he would have had a valid self-defense claim.
He was trying to run away while his attacker advanced on him. The defendant has no legal or moral claim of self-defense.
Complain all you want, but this is what separates us from North Korea, and it's what makes ours the most legitimate legal system in the world. So many people on social media would like the state or public opinion to be empowered to declare someone guilty with only limited due process. That's bullshit and it's what makes a totalitarian state.
In the US we give the accused every possible refuge, every possible opportunity to defend themselves, even the right to make bullshit claims. The decision can, and should, be made by a group of their peers who have access to all of the evidence, under the guidance of a judge, with no undue influence, no pressure from the public, and no way for the state to intervene.
Few things irk me as much as people who see a court decision they don't like (Rittenhouse, etc.) and then decide the problem is that the courts must be reined in and better controlled. Nope. Go move to North Korea or Eritrea if that's what you want. There are no political prisoners in the United States.