It makes little sense since there's robots in the tower and they aren't trying to kill you. Why are the jungle robots rabid and camp inside a vault?
It also doesn't make sense that you can be a robot and the robots want to shoot you.
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The bots in the Tower and the Vex are two very, very different things. The Vex ate minions of the darkness, origin unknown. They are going from planet to planet and basically converting them into machines. Bots at the Tower were made by man to push brooms and serve as vendors. Big difference.