I have a hard time envisioning 'emotionally damaging truth'. More truth is always better, even if it is uncomfortable. Operating on un-truths can be damaging, truth should allow you to function better, not worse.

The problem with this story is that effectively nothing had changed that wasn't already there.

I found out my dad had been married prior to being married to my mom. It's a long and interesting story but it never made me think less of him (insofar as that was still possible), in fact in some ways it redeemed him and made me understand him a little bit better.