[quote=@HEAVY METAL]
Page 18 5E PHB 

....And a "BURNING HATRED" for Goblins & Orcs......
[/quote]
True, I kind of glossed over that since it didn't explain how or why beyond the obvious.

Citadel Felbarr had a population of a quarter million Dwarves so even if it was just that, being able to point to a Dwarven equivalent of 9/11 or something felt more explanatory.