If it was a trap, he wouldn't feel the slightest bit of heartache if these Earth Demons were killed.
Weak members of the Earth Demon Alien Race were expendable. If they died, they died. A new batch could be raised in no time.
These creatures without potential were just a drain on Cultivation Resources.
The Demon Tribulations launched periodically from the Demon Cave were for this very reason: there were too many Earth Demon Alien Race members with no potential, and the underground Cultivation Resources couldn't support them. The only solution was to initiate a Demon Tribulation to cull some of them. Those who could grow stronger would naturally seize the opportunity to do so.
As for those who didn't... they could just die.
"Your Majesty, the Demon Lord, is brilliant. You see through all the Human Race's schemes. Their contemptible tricks are beneath your notice!"
"In that case, Your Majesty, which Demon Army will you assign to the upper levels of the Demon Cave this time?"
