While I understand the point you're trying to make, Tedronai, I think context is important here. Due process is obviously an essential cog of the justice system and 'innocent until proven guilty' is just one of those things that set America apart from many other countries in the 21st century. The visceral reaction, however, to the murder of those innocent people, shouldn't be characterised as evil. If you can apply the concept of innocence until proven guilty, you can also apply it to Zuriel & co. A gut reaction isn't an action, nor is it the will to commit murder & bypass due process. A gut reaction, however strongly expressed, is not enough grounds to be called evil.
Clearly it wasn't thought through and obviously if they do take matters into their own hands and try to mete out their own justice upon others, then you step into a completely different territory.
I think, however, that the characterisation of the slowness of justice and its process shouldn't be the sole burden of the US's public institutions. While justice and trials can take time, it can take much more time with good lawyers and lawyers aren't a public institution, it is a for-profit profession and if you are to blame the justice system, then don't lay it all on the government's doorstep.
Justice isn't a slow process because of the government or because of lawyers. Justice is a slow process that takes time because both sides are to be heard and given a chance to prove their innocence/claim. While individuals may want to mete out punishment asap, it is not an appropriate replacement to due process. I understand the visceral reaction to the tragedy, but somewhere along the line, you have to resist the urge. Your eagerness to deal punishment is in direct contravention to what the US justice system has been based on all those years.