[quote=@POOHEAD189]
<Snipped quote by Willy Vereb>
I guess rejecting the Ancestor Gods is enough to be seen as "undwarfish." 
>breaking Oaths 
>breaking traditions/changing culture drastically 
>being cowards 
>stealing 
>heretical religious practices 
>consorting with Orruks or Beastman (maybe Uruks too) 
>Attempting to practice/consorting with foul magic 
>becoming mutated due to such practices 
>marrying outside of the Dwarf race and procreating with other races (Manlings from Rhun might be ok in very very small doses...MIGHT)

to name a few
[/quote]Damn, those are pretty strict laws.
My Duergar (or Yngvarians as they call themselves) reject the ancestor gods and rather revere the god Yngvi (their name Yngvar would roughly translate as "protected by Yngvi") but said god never did anything openly to them. They are also far less honor-bound and not picky in their clients to trade with. They might be also infamous for their mercenaries that travel the world and lend their services to all takers.
So yeah, while not glaring opposites like the Chaos Dwarves they would be perhaps considered by your people almost just as bad.
Hence their name as Duergar.