When i go into the fort to get the chip the guards there say that the mark of caesar protects me. Yet they still attack me. Is this a hint that i need the mark of Caesar to be welcome there or is it a bug?

This happened to me too. I had to start a new game which i was gunna do anyhow so it didnt bother me.

ANYHOW...You're screwed.

:)

Shoulda killed when you had the chance. I did on my 2nd playthrough to avoid this glitch

same thing happened to me what i did was when they attacked me i just let loose and killed them all found the centurion and collected his armor put it on and went to the fort no one attacked me so i made a b line for the tent and when i got in they all attacked me i found if u kill one of them and use the ballistic fist against them you'll be fine if you know how to use unarmed effectively and the chip is found on ceaser's corpse than all you have to do is run to the bunker kill everyone that bothers you finish up down there and just fast travel out once you're done

it's pretty easy but good luck if you try this since its kind of a hassle

Thats just it. Theyre not attacking me down by the water. They attack me once i go through the gate and into the fort. Where is Centurion at in there?

Attacking Legionaries, or otherwise gaining Caesar's Legion infamy, will make them hostile towards you despite holding the mark.