As I said in my third paragraph, I think that particular question is some way removed from the points originally at issue in this discussion. But to both of those my reaction is "well, kinda". In more detail (reluctantly because I think it's a big digression):

• If two people are in a longstanding sexual relationship and one suddenly withdraws consent, clearly something has gone badly wrong. The same is true if one has been working for the other for some time and suddenly gets fired.
• Having sex when you really, really don't want to is much worse than missing out on sex when you want it. Having no job is much worse than having one employee who isn't performing well. This is an important respect in which the analogy breaks down.
• People should be able to fire employees and to refuse consent to sex.
• They have a moral obligation to do so in as reasonable a fashion as they can.
• In some cases that may still mean doing it suddenly (e.g., you find that your partner is violent and dangerous; you find that your employee has been embezzling; you contract a medical condition that makes sex agonizingly painful; your company loses a contract and suddenly has no money).
• Because losing all of your income is generally a big disaster, much worse than having to pay one employee's salary, it is reasonable to require employers not to leave their employees completely screwed if they get fired unless it's because of the employee's serious misconduct.
• Because being forced to have sex on one occasion is so much worse than being denied sex on one occasion, it is reasonable to say that if one partner says no then the other is obliged not to force sex on them. (But because being denied sex on all occasions is bad, it is also reasonable to say that if one partner is consistently refusing consent then the other is entitled to look elsewhere, even if their relationship is notionally monogamous.)

I don't see any inconsistency in the above; my positions on the two questions aren't identical, for reasons tightly bound up with the ways in which the two questions themselves aren't identical.

"a boss has the right to fire anyone at any time"

In the US that's already the case and even the people who don't think that wives should be allowed to refuse sex from husbands seem to see nothing wrong with that. Well, except when someone is fired is for saying something factually correct but offensive.