The presumption of innocent until proven guilty can be sorely tested. You don't have to arbitrate, heal or solve this problem alone. Survivors need support not rescue. You will be helping yourself if you first look at your resistance or denial. Know your own biases and prejudices.
Most survivors never tell anyone that they have been assaulted.
If someone tells you about their abuse, consider it an honor. You may not feel lucky but you are. Welcome to a very confusing, murky world. Believe them-they are telling the truth. Tell them you're sorry and it wasn't their fault.