By definition, assuming anything at all requires that there is no evidence. If you have evidence, it's not an assumption. Also by definition, some things must be assumed. No one has ever managed to construct a system without assumptions.
vis-a-vis the specific issue of "innocent until proven guilty", it really is a legal principle first-and-foremost though, designed to avoid the specter of state-sanctioned tyranny and injustice. The court system as constructed strongly prefers letting the guilty go free over innocent people being imprisoned by the state, at least at its theoretical base (how it works out in practice is another matter). There are systems which do not do this, and assume guilty until proven innocent. It is not obvious to me why society should necessarily prefer letting the guilty go free (and all that entails) over punishing the innocent (with all
that entails) with regards to groping, which is the specific issue we are discussing.
It doesn't matter how corrupted it becomes, this is the mindset that we are supposed to take to EVERY allegation of wrongdoing. And ignoring this basic principle is seriously damaging our entire legal framework.
Already addressed. Our legal system is an extension of our society and is representative of the way society views itself, intentionally ignoring a very sound principle such as innocent until proven guilty is just a plain bad idea.
Which is why people love and respect lawyers, right? Because we see them as extensions of ourselves, and not guardians of a mystical, archaic forces of dangerous power?
It's unclear to me that society must act exactly as the state does and follow the same principles thereof, which is what you are implying. I believe an argument could be constructed such that state should act differently, precisely
because it is the state and not society.