What the Heavenly Demon Palace Lord said was both right and wrong.
The Emperor Dragon was not an innate dragon god like the Primordial Two Dragons, but an acquired achievement. Only by truly subduing all dragons could one attain the Emperor Dragon Body.
The Primordial Two Dragons were different. They were born innate; if something did not exist innately, it could never be achieved afterward. But if it existed innately, then so long as one did not die young midway, one would surely accomplish immeasurable feats.
Strictly speaking, true dragons such as the Green Dragon, Red Dragon, White Dragon, Black Dragon, and Yellow Dragon all had the qualifications to contend for the Emperor Dragon Body.
It was like the rulers of the human race: they could inherit the throne, or they could be common folk who raised armies in rebellion and won the world through conquest.
Take Liu Bang, for instance. Though he possessed the body of a Red Dragon, as the founding ancestor of the Great Han Dynasty, inheriting the First Emperor's legacy and subduing all under Heaven, he embodied the culmination of the imperial path. Thus, the path he walked was the Way of the Emperor Dragon.
Meng Zhao bore the Purple Origin Dragon Body, a fusion of the Ziwei Treasure Body and some kind of Dragon Body. In truth, he really did possess something of the caliber of a Destined Emperor Dragon.
Therefore, while the Heavenly Demon Palace Lord's words were somewhat biased, they were still eight or nine parts out of ten close to the truth.
The Emperor Dragon was not a bloodline, but a realm. Meng Zhao's bloodline and physique merely came infinitely close to such a bloodline, giving him a few advantages!
As for Beitang Shu, with the groundwork laid beforehand, he did not