I have been neutral to Caesar's Legion, and have not done anything to make them aggressive towards me. I went to see the enslaved Powder Gangers, but I didn't set them free. The Legion was nice to me.
I didn't see any Legion members until I reached New Vegas and was offered an audience with Caesar himself. I received a coin and was told to go meet him. I fast-traveled back to the location with the slaves and the Legion had turned hostile to me.
After killing them, I continued onwards and met more Legion that weren't hostile, started talking to me about the quest, and who then became hostile.
Anyone have an idea what happened?