Blow up brotherhood base???

You can do everything for the Brotherhood and then blow them up, I think they only have four or five quests. All I know for sure is

-spoiler-

If you go with the NCR questline, you HAVE to kill the Brotherhood.

Well you dont have to i found out, you can talk the elder Mcnamara(?) and he'll send people to help you.

KEY CARDS there is 3 of them 1 captin of the palidin 2 the elder and 3 a guy in a red robe but i forget his name srry :(

If your working for Mr. House you have no say in the matter, you have to blow up the bunker. Same goes for the Legion. If your working independently or with the NCR you have the option to save them.

Yeah i was messing about and i actually did blow up the bunker, and then went back down into it after to where the intercom is, and there were actually members of the brotherhood on the other side like fully active and alive trying to kill me, like in the rubble haha. glitchyyyy.

Oh and i didnt need the keycards, i think if your skill is high enough you can just over ride it, using a computer next to i think with your science skill.

To do what kaleidoscopekid suggested and hack the terminal, your Science Skill has to be 100. You can either raise it all the way with skill point expenditure or you can raise it to 80 with skill points, then use a Programmer's Digest to temporarily boost it to +20 (IF you have the Comprehension perk) and then try to hack.

yeah i often carry a followers lab coat which boosts your science by 5 aswell as doing what JupiterRex said, just incase im five short, as science is usually one of the last things i level up, which i dont recommend haha.