In this mindset you've setup a guilty until proven innocent framework because in your mind you already believe to be true any accusations leveled at someone.
When someone levels an accusation, the only belief you should hold is that it's a serious accusation that needs further investigation because someone has risked a lot by leveling it.
Believing anything that comes out of someone's mouth to be true when there are massive consequences to their words is unethical.
>It's fine for people to say "I think he did it, but the prosecution didn't prove it, and so I found him not guilty."
You cannot believe someone to have done something and personally believe that the person is not guilty. They may not be guilty under the framework of the law, but you are still treating them as guilty in your mind. If you worked with the accused and you had a strong sense of ethics, you would never treat that person the same way again, even though the accusation may have been proven to be fabricated.
It is unethical to take accusations at face value that will ruin people's lives.
Believing a colleague when they come to you with ANY complaint does not mean you're going to pass judgement, or you even have to. It means listening and doing that in a way that does not discourage future complaints.
Your attitude towards them -- listening etc -- is a completely orthogonal matter to whether you believe in the truth of their claims.
There seems to be this wishy-washy notion of "belief" that's causing confusion in this thread, where "believing" is equated to "not being judgemental".
That's not "belief". Believing X means thinking that X is true. What you're really talking about is taking an agnostic position.
It's fine for people to say "I think he did it, but the prosecution didn't prove it, and so I found him not guilty."