My first thought was, "Just use anything from the experimental literature on the Coase Theorem," but then I realized most people wouldn't be able to easily rationalize Coasean results. However, if you think otherwise, the divorce literature is interesting. Perhaps not clear-cut enough.
"Facts about happiness" really is a good idea, here are some suggestions off the top of my head:
"Money doesn't buy happiness" is true even across countries with huge differences in wealth and income. (False. Rationalization: Simple folk wisdom, right? Why wouldn't other people around the globe have come to the same conclusion?)
More direct participation in democracy has a negative effect on happiness; more representational institutions increase happiness. (False. Easily rationalized: "Representational democracy woo!" I figure most of your audience will be American. More seriously, "Less stress: you have to worry about technical policies less often and vote less often, but your voice is still heard." )
Women are, in general, happier than men. This effect appears to last over time and cross-country. (False. Could be rationalized as, "women work less, have better social lives, are less materialistic, or female modes of thinking manage stress better.")
Unfortunately, these are contentious examples, and you may want something with more rigorous empirics to make your point. But then, you shouldn't go near happiness research to begin with.
I'm writing the section of the rationality book dealing with hindsight bias, and I'd like to write my own, less racially charged and less America-specific, version of the Hindsight Devalues Science example - in the original, facts like "Better educated soldiers suffered more adjustment problems than less educated soldiers. (Intellectuals were less prepared for battle stresses than street-smart people.)" which is actually an inverted version of the truth, that still sounds plausible enough that people will try to explain it even though it's wrong.
I'm looking for facts that are experimentally verified and invertible, i.e., I can give five examples that are the opposite of the usual results without people catching on.
Divia (today's writing assistant) has suggested facts about marriage and facts about happiness as possible sources of examples, but neither of us can think of a good set of facts offhand and Googling didn't help me much. Five related facts would be nice, but failing that I'll just take five facts. My own brain just seems to be very bad at answering this kind of query for some reason; I literally can't think of five things I know.
(Note also that I have a general policy of keeping anything related to religion out of the rationality book - that there be no mention of it whatsoever.)