I have a suspicion that VEX do not understand other lifeforms... For instance... The scene with the captain of the Exodus Black. They are testing emotions... Anger and fear are easy..... Even revulsion. Happyness is more subtle but easy enough to understand.... Loss... I do not know that Vex understand the concept of loss...Partly because being quantum entities, they see forward in both directions. You can change the past by modifying the future and change the future by modifying the past. They do not view things in a truly linear fashion. So the concept of loss and sorrow may well be very alien to them. That which was is will be. That which is and will be shall have been. They have no reason to have a concept of loss.... They may in truth be trying to learn to understand a universe which is linear, and it is possible that the reason we find them so abhorrent is because they simply have not come yet to understand that time is linear for everyone except them. One could even argue that many events in the campaign are being portrayed as from the observation point of the vex. Events being inspected and reviewed over and over with different participants in different timelines. The vex... I am not sure, want to be "the enemy"... Nor our allies... They have by and large entirely avoided earth even though they absolutely could take it in the space of hours. It would be as simple as an exertion of will. And yet. We have never seen a single VEX construct on earth.