Well, Im doing the Dealing With Contreras unmarked quest, and I decided to , but then my NRC fame dropped to Shunned, Boone warned me and stuffs, well, no danger I thought, I got my NRC outfit on, and now I'll just be on my way to McCarran.
Well when i arrived outside the gate, the guard started shooting at me, I shot him, Boone left me.
I loaded back, did the same thing, and tried to go to Sharecropper farms, and go from there to McCarran, but thats NRC territory, and Crimson Caravan guys started shooting, farmers attacked, NRC Troopers attacked.


Is this just a bug/glitch cuz all the time i was wearing the NRC armor?

Guards see through your armor.

Some guys can see through disguises and if you kill ANYONE from hidden mode you can avoid faction loss.

This. If you want to avoid losing rep, the only way to be sure is to sneak and not let anyone see the deed.

I killed Keller but suffer no rep hit....maybe because he turn on me first?

Killing Keller BEFORE he turns on you makes you loose rep and karma with the NCR.