With the Brotherhood, I generally shoot anyone who has any inkling of being a hostile faction. The tag does matter. I, and the other Brotherhood pilots will still shoot you, just for having the tag. My character especially doesn't like foreigners in his system, and having an Outcast tag only makes it worse. If you truely want to be neutral with both, become a junker. You will probably be attacked by the GoR if you havd that setup but with a Corsair tag.