Here are some arguments that I think would work for someone like me:
"Men love orgasms so much (or think they do) that it may be hard for you to imagine that some women don't care about having orgasms, or that some women might actually DISLIKE orgasms."
"Do you like to continue vigorously pumping away after you have your orgasm? [In my - CF's - case, I don't. It feels unpleasant, an overstimulated feeling like being tickled.] Maybe that "overstimulated" feeling is like how I feel when you try to give me an orgasm. I don't like being pounded. I really don't much care for the feeling of orgasm itself, either. I'd much rather you just be gentle with me. I like the feeling of you inside me, and the feeling of gentle pumping. I also like it when you lie still and just cuddle (as long as I'm not getting crushed by your weight). I like kissing and touching, etc. I don't want or need to have an orgasm. Please don't try to give me one."
"You know how a woman can be an angel for most of the month, and then mysteriously turn into an evil witch (or another word that rhymes with "witch") a few days before her period? That's what hormones can do to women's brains. That's what orgasms do to me. They release chemicals that poison my brain and, over the course of the day after the orgasm, turn me into the Wicked Witch of the West. Trust me, you won't want to be anywhere near me if that happens! I won't want to be anywhere near me if that happens! And I'll blame it all on you. Don't say I didn't warn you. So, don't worry about giving me orgasms. I DON'T WANT THEM!!!"
If all else fails, wear a T-shirt with "What part of 'I DON'T WANT AN ORGASM' don't you understand?" while recovering from the hangover.
Here are some links to related material:
Persephone's experience: Hold the orgasm, please, Day 4 Tsunami recovery, and Hangover
Mitsiky's experience: Things fall apart
Mitsiky's Alternate perspective
Marnia recommends: The Big 'O' Isn't Orgasm