This hit a bit close to home for me because I've been having a discussion/disagreement with my SO, in which this scenario was basically my fear. This is going to sound stupid and paranoid in comparison, but she's leaving the idealistic industry in which we both met and worked to go to law school, and I was scared that the financial pressures of loans and her new peer group might lead her to take a job that I wouldn't be able to accept. She thought that I thought she was going "evil," and was hurt that I thought she was capable of doing something counter to the values we both share. Finally I realized that the reason that she wants to leave her current job is because she feels it's ethically dubious and she's disillusioned with the industry, and the chances she could be happy in a law firm doing morally ambiguous work are basically nil.

All that said, I really sympathize with your position. I think that some couples can together agree that their respective jobs are kind of "all in the game," and still stay together. I guess James Carville and Mary Matalin are kind of the standing example. Yet this might be the exception that proves the rule that usually this kind of relationship is infeasible. If I were in your position, I would have a really hard time being okay with this.

I can understand if he's cynical and disillusioned with the work and feels that if the system is shitty, then he might as well get paid. But this tendency of private interests to purchase its antagonists is part of what makes the system shitty, and he's playing into it. The revolving door between the financial industry and its supposed government regulators is part of what has led to a corrupt financial system and a general lack of oversight. It sounds like he might have given up on the fight and is now just looking out for his own (and possibly your) personal benefit.

I think it's understandable if you decide that you can't accept this. But you probably should try to fully discuss things with him and see if you can explain your feelings, that it's not about the money, that you feel that his new job is to directly undermine a cause that you really care about and that you've put years of work into. Also, I think it's worth trying to understand why he's okay with taking a job counter to his previous work - is it really just about the higher salary? And probably making a special effort to be calm and empathetic and not say mean things would make for a good foundation for a productive discussion.