Someone told me way ago that they would like me no matter what, even if I did a total 180 and turned evil. An innocent phrase but it got me the player thinking - "hey, I never had an align change yet, not necessarily with this char but I'll try eventually..." Sure enough I remembered that again when I got a bloodoath offered to me. The situation warranted a possibility to come up with an IC reason as well, I just couldn't pull it off consistently.
P.S. I do hate a few fort imms oocly. But going Empire wasn't merely a way for me to vent that hate.