Getting a letter like that probably wasn't as shocking as traumatic as we may think. Ignorance like this is a character trait that isn't easily hidden so I'm sure throughout the receiver's life, he saw that side of his father frequently. It does not make it any better, just a reality.

I hope the receiver has been able to come to terms with the "loss" and I hope he's been able to be resolute in his approach. There's really no other way to be.

If it was me, I would frame it and constantly tell myself and anyone who saw it that that is NOT the way one should view others, much less family. And it would continually push me to just be that much better each and every day. I would not allow it to defeat me.