Goku was not looking down on the identity of demons when he said this.
The Demon Clan and the Heavenly Court were getting along peacefully now, but they still required demons to cast off their identity as demons—not by becoming officials in the Heavenly Court or immortals in the heavens, but by purging the evil demonic aura from their bodies.
If that evil demonic aura remained in one's body and one's strength continued to grow, heavenly tribulations would strike far more frequently—several times more often than for ordinary cultivators. That was why there were so few powerful demons; most died to heavenly tribulations before they could reach that point.
If one cultivated into immortality, the evil demonic aura in one's body would gradually dissipate, and heavenly tribulations would descend less often.
Cultivating into immortality did not necessarily mean becoming an immortal in heaven. Immortality was a realm, not an identity.
As many demons cultivated, they would gradually eliminate the evil demonic aura within their bodies. But the process was extremely difficult, painful, and slow.
Thus, quite a few demons gave up on it and instead relied on their evil demonic aura to increase their strength.
Now that the Heavenly Court no longer harshly suppressed the many demons of the Three Realms, they had plenty of time to dispel the evil demonic aura from their bodies and avoid being slain by heavenly tribulations in the future.
Yet it was difficult to do this alone. If someone specialized in helping remove evil demonic aura, it would be much easier.
Marshal Canopy was slightly stunned upon hearing Goku's words. This truly would be a good thing for him, but he did not agree. He continued fighting Goku.
After leaving Gao Family Village, Little White Dragon headed north. He searched for a long time