You’re potentially harming an innocent person either way. Ideally, evidence would allow you to make an informed decision about who is most likely the innocent party. But in the absence of that, trying to remain neutral is supporting the more powerful party. So, rather than defaulting to the status quo, I apply rule-utilitarian principles: behave as would cause the least harm if treated as a universal rule.
Indeed! Which is why, in a context where we’re determining guilt and assigning punishment, the rule with the greatest utility is “innocent until proven guilty.” This isn’t that context though. This is an interpersonal context. We’re not trying to determine if Mearls deserves punishment, we’re just deciding whose word to believe when two people are in conflict. And in that context, I believe the rule with the greatest utility is to believe the word of the (alleged) victim.
But I’m not ignoring “innocent until proven guilty.” I’m saying it’s not the right rule for the context.