I'd prove that the human race is worth saving by beating the alien's fleshy forehead in with a mallet and sending his lifeless carcass back to the mothership as a message to the rest of them.
Yeah, have him transport to a location where all the armies of the world are waiting to murder him/drop nukes on him, etc.
I don't know whether the majority of the human race should live unless they change their view of the world (i.e. believing they know the best and only way to live, etc).