Call ME old fashioned, but I consider a marriage certificate (or its equivalent) an eternal consent form. (At least until death or divorce do you part.)
You say that as your defense in court, and I'll vote to convict on a charge of rape, no question. That's an indefensible attitude.
Settle down, I'm not a rapist. Naturally I respect everyone's right to say no, even though I don't quite understand it. If you're not happy with your spouse you need to get that shit sorted out and if you can't then just seperate. I get that this is an unpopular opinion and that I'm an easy target for a SJW, but if you are in a happy and healthy relationship, explain to me the reason for denying your partner sex. If indeed you are just too tired or not in the mood it still won't kill you to sacrifice a few minutes to keep your partner happy.
Instead of just saying no means no, which I've already admitted that I respect, perhaps you can better explain your reasoning behind why you would refuse sex to your partner, while still maintaining a healthy relationship with them.