In this case it was obvious why to divert because the drunkards were not under control. But what always make me wonder is those cases where they say that the unruly passenger have been restrained and fastened to his seat. I understand it like he then is no longer any risk to safety of the aircraft. Then why do divert to another airport and make the rest of the passengers suffer. Or is it some theory I have missed somewhere that say we still need to divert even if there is no longer any risk to safety?
Normally I believe its up to the PIC (Captain) to decide, but I wonder with all those cases where drunk passenger have been restrained and secured why divert and make all the other passengers suffer if there is nothing that would make continuing unsafe.