Page one of the site arguing defendants are guilty has nothing that would count as evidence for guilt.

I agree. A lot of the stuff on that site was just silly. It was mostly appeals to emotion and random stuff like (I'm paraphrasing), "A witness heard people running on some metal stairs, therefore the defendants are guilty!"

Aren't there enough opportunities for us to practice rationality such that we can check our answers to make it mostly a waste of time to assign probabilities to an event for which it will probably forever be impossible to know "the answer"?

I think this is a test to see if we all come to the same conclusion in a case that stirs up a lot of emotions. If komponisto is Italian, he might have vastly different probability estimates than some of us Americans.