Seeing the Golden Dragon crush and slaughter a drow matron on the spot, all the clan leaders chose to remain silent, even though none of them knew of Noah's noble bloodline as an ancestor—because they had never seen a Golden Dragon, their understanding of the Golden Dragon was limited to rumors, and of course, they couldn't recognize an ancestor.
The overwhelming power displayed by the Golden Dragon now also matched their perceptions of the Golden Dragon, except for the cruelty of the slaughter, which was somewhat more brutal than the rumors suggested.
However, given the target, it's understandable, because the legendary Golden Dragons are known to detest evil and show no mercy.
In other words, when this Golden Dragon declared that it intended to kill them all, it was not a threat; it truly intended to do so.