If my employer wants me to work off hours, I mean maybe I will, if I don't have anything going on, and I'll take some time the next day where I won't work as compensation for doing that, I won't ask permission.
If I do have something going on, I'll say, "Can't do that. Have something going on". They're fine with it. They're reasonable people. Why would I work for unreasonable people? I would work for someone else.
If they actually did fire me? OK, maybe I look for another job, but probably I'm retired. I saved my money. I negotiate from a position of strength.