Michael was not joking, he was truly planning to bring an end to the Tuolu sect.
More than just because of the girls in front of him, it is for the sake of the earth!
The events here will eventually reach the Tuolu sect's headquarters.
By that time, they might enter the tomb to investigate, and hence, they might discover the existence of the spatial passage!
Once the spatial passage is discovered, the members of the Tuolu sect could cause havoc on earth, which is the last thing Michael wants to happen.
In order to avoid this situation completely, he needs to make this island his own!
And yet, this island belongs to the Tuolu sect!
Therefore, what Michael truly wants to do is to take this island from the Tuolu sect, but ironically, this happens to be the graveyard of the previous leader!
He just recently learned from a guard that this previous leader is the father of the current leader, so how could they willingly give up their father's graveyard?