His second point after the joke sounds solid enough for your problems though, it's like 1+1 = 2.

yeah i killed some legion guys. So there is nothing I can do about it ?
I was attacked by them when I entered that town they burned down at the beginning.

Really don't want to start over the whole game now that I invested 15 hours. Maybe there are cheats or something I could do ? Also why am I still being attacked although im told that my actions against the legion have been forgiven after leaving the casino with the platinum chip...its just not the case.

If nothing can be done about it I will most likely have to wait until a PC User (Im playing the xbox 360 version) will send me one of their savegame at some similar point in the game and Ill have to get the pc version too...

have you tried wearing that faction's armor before approaching them?