4.) I think Andrew Cohen is right -- trials don't work as strict "moral surrogates." Not everything that is immoral is illegal -- nor should it be. I want to live in a society that presumes innocence. I want to live in that society even when I feel that a person should be punished.
Trials are nothing but moral surrogates, and have been for a long time. The two big components of trials have always been in tension, and that tension has been more precarious in the US than is commonly admitted: there are procedural rules that are to be followed--presumption of innocence et al--and whether the outcomes are just. As it turns out, people have very little patience for procedurally legitimate but unjust outcomes.
Justice is the tail that wags the dog: if the outcome of the trial is deemed just, then procedural questions are minimized or overlooked; if the outcome is 'wrong,' then there must have been a procedural error somewhere. (Trial procedures being what they are, there's frequently such an error to latch onto.) To see how this works out, one needs only look back as far as the DOMA and Prop 8 rulings: what matters to the vast majority of people is that the outcome is 'right.' The legal nitty-gritty and the further consequences of the ruling are immaterial.
That America has a commitment to the rule of law, the presumption of innocence, and all the rest, is one of those stereotypes that we tend to believe without much reflection on whether these enter into the actual reaction to cases as they arise. Assuming that people will react to trials as moral surrogates explains pretty much everything we see.