I'm not justifying it. Im showing it's normal and understandable. I am thus saying that those who think or believe it's not are deluded.
If you believe an organization should or does give a 100% or even 90% acurate historical record then you have a false belief and thus keeping that belief makes you deluded and surprised and upset by it.
It's not just an abstract "organization" - it's people that you've known as friends and teachers for years who lied to your face and in writing.
Now, maybe believing that everyone your know is lying to you by default keeps you from being "deluded and upset" - but it's no way to live, in my book.