What aspect of what I'm saying is irrational?
Lets try an example from my own life:
I've got about a bit, not as much as some, not as little as others, and I am a woman.
I have had a boyfriend, who liked a finger (or two) up his bum. So, sometimes, I would oblige. At all stages of this process, I would only continue if he wanted it. I knew that he was giving full consent to this process, both when we were having sex sober, or drunk.
Other boyfriends have not enjoyed this, so I didn't stick a finger up their bum. At no point did I get confused or mis-understand and accidentally stick a finger up their respective bums.
I did not find this tricky to navigate as a concept, when sober or fall down drunk. It seems reasonable to me, that I would only stick things in someone else's orifices when they definitely wanted me to.
Now. I would say that that is reasonable behaviour. Don't stick bits of you in bits of other people unless you are sure they want you to. If you do, and they didn't want it, then that is rape (or sexual assault) - and they get to decide that, since it's their orifice - not you, not the person who is doing the sticking.
Sounds rational and reasonable to me.