You continually use the word steal. GMs will rectify situations where NMs are stolen, period. The problem is, we are not talking about stealing.
Ex1:
Group A is fighting Nidhogg.
Group B's Paladin casts Cure 1 on Group A's Paladin.
Group B's Paladin proceeds to 2hr/Sentinel/spam his Enmity up to cap.
Nidhogg moves out of range of Group A's Paladin, and goes White due to Disengage.
Group B's Paladin casts Flash and claims Nidhogg because he was on the hate list.
Nidhogg was stolen.
Ex2:
Group A is fighting Nidhogg.
Group B waits patiently nearby, but does not act on any member of Group A.
Group A's Paladin dies with sole claim, there are no other melees hitting Nidhogg and no mage casting on it.
Nidhogg goes White.
Group B's Paladin casts Flash then uses Shield Bash before anyone in Group A acts.
Nidhogg was not stolen.
This is the distinction that GMs made over the years, and has nothing to do with race. As far as they are concerned, unless there was foul play involved, any transfer of claim can be considered legitimate.