I'm having troubles fulfilling my dreams of evilness [early game spoilers only]

Basically, my goal as soon as I heard about all the factions in this game was to be evil. I've assisted the powder gangers in taking over Goodsprings, somewhat out of evilness but mostly because Ringo was a real dick, despite wanting my help.

I then helped the powder gangers in their prison complex by defeating an NCR raid, gaining infamy with the NCR (which is what I wanted, because I'm planning to help Caesar's Legion in whatever way I can). My problem is that all that infamy I gained with the NCR seems to have not helped me out at all in my quests for evilness - yesterday as I walked to Nipton, I was confronted by a ranger who gave me three days to become a good person in the eyes of the NCR.

I'm so confused, because it seemed like an automated thing (they just appeared out of nowhere). Does this mean I have no hope of becoming a revolutionary against the NCR?

Please don't spoil anything, but my plan is now to wait the three days and kill the ranger when they come back. If I need to do stuff in Novac, I can just wear NCR army gear and be treated as neutral, right?

Please just give me an indication of whether I should actually listen to the Ranger and be good for a while or if it's possible to kill her and move on without giving away any story spoilers. It's a big ask, but I'm worried that this sandbox RPG is really just a support the NCR RPG