I have to imagine it’s a very difficult thing to cope with; learning something like that about a very close friend. It has to really mess with you. And I can understand the human instinct to want to defend them regardless of your moral standards.
I personally don’t think this goes to show any moral failing on their part. Or at worst, whatever moral failing may be present is mostly due in part to a natural human reaction to complex emotions better dealt with in therapy. As such, I think these two should be afforded a bit of leeway.