So im playing NV having a great time and i get to the quest "you'll know it when it happens" and im looking to do this quest right, then when i walk out on the observation deck like im supposed to all of a sudden they start shooting me and all of a sudden im vilified. Like what the hell happened, I was having a great time then this. Now i can't switch sides to legion because i was vilified from there on purpose cause i don't like them so im stuck like what do i do? My NCR tag thing is Warm-hearted Devil.

By observation deck, are you talking about the roof with the vertibird? You aren't allowed to be up there without clearance, and you will get shot if you are caught up there.

I can't say I've ever done that quest with as low of a reputation as warm-hearted devil so I can't help you there. Perhaps do some side quests to bring up your NCR rep?