These are board members. They are not hired in the first place, and generally need to be re-appointed every few years. This law has been slowly ratcheting up, so either people have simply been not re-appointed to the board, or they have increased the size of the board to include new members who were chosen from more diverse backgrounds.
It doesn't mean that at all. You can hire a black person and not fire anyone. They may choose to fire someone, but given these are board positions, and it literally takes just one person -- they can easily accommodate simply hiring someone.
If that was the literal rule (you had to fire a white male) then yes, I would be against it. The intent isn't to be spiteful against white males. It's to give space at the table for other groups that are intentionally excluded due to their race.
No one was fired.