Why can't I compare the murder of these two young brothers to what you're proposing...?

It's all about protecting the greater good and exacting vengeance for those in the community who can't, right...?

I'm sure the sick mofos involved in Emmit's & Trayvon's deaths felt that they were
"in the right" too, just like you propose...
One died because a group was "protecting" the purity of White women and the other died because a man was just "protecting" his neighborhood...

Street Justice, right...?
As for the example you put forth. I can only say it's not an easy situation to assess.
It's clearly an emotionally charged example you presented.
My answer:
How are you avenging your family if you run into said restaurant and shot him in the head, and now
you are the one in prison?
How many driveby's have been conducted in the inner cities around the country and the culprits are still at large? Should
we go kill the shooters if the police fail to find them?
What judge is going to look at your case and say; "I understand your motives. The charges are dropped. Case dismissed". It's not happening.

- The system is
NOT perfect.
- The system fails.
- The system needs to be overhauled, retooled and remade.
But until then, it's what we've got and we have to live within it until
we can change it.
Curious:
You never answered my question about "What if you're wrong?"