For many conventional things that are considered standard “stereotypes” about groups such as physical appearance-related assumptions about sex or gender, age, race, nationality, or style of dress, accent etc., that the general public employs?
On the one hand, those in the rationality community emphasize the point to use whatever information possible, and that means sometimes using statistical info that would be called stereotyping (the famous example of statistical discrimination being car insurance for men and women, and other practical things such as avoiding tall men in dark alleys but not short women).
However, rationalists often also emphasize updating priors so it could be that even if initial stereotypes are held, a big deal is made of when to update more readily—for example, when many people would keep on stereotyping a member of a nationality for e.g. not fitting the stereotype (e.g. are you really an X if you don’t look like the X’s I know, or have an accent I associate with X, or eat what I think of as X food?), it may be rational to update more readily (I just met a X person, I should update my preconceived notion of what X’s are like instead of insisting they’re not a real X for not following my stereotype).
Also, self-described rationalists are famously big on individualism (e.g. Scott Alexander’s discussion of respecting individual preferences such as introverts vs. extraverts, ask vs. guess culture which is more about individual preferences than traditional demographic categories or cultures). It may be the case that some stereotypes are true on average (80% of X like some food vs. only 40%’s of Y’s) but having an individualist, analytic mind (typically seen as more a WEIRD thing or STEM thing or “rationalist” thing, perhaps, though not always) vs. a collectivist, hollistic one might laser focus on the individual’s agency and preferences (e.g. I don’t care if Bob’s a member of group X that stereotypically likes the food, Bob has already told me he doesn’t like it, I’ll take his word for it).
You use all data you have. That includes your previous experience with people who have a trait X, your previous experience with people who told you what opinion to have on people who have a trait X, your current interaction with the specific person, etc.
Is it important for you to make more correct conclusions? Get more data.
I think it goes without saying that more data is good. But the quality or strength of the data is important too. I think some debates over stereotypes rest on if they count as good quality data, or data that should override other data (firsthand experience) on how to update your prior. For instance, if you get data from mass media that “all women like chocolate more than men” but get data from most of the men and women you know that both like chocolate equally, which trumps which in if you are more likely to consider chocolate as gift to male or female friends?
You could say the societal stereotype is better data—after all stereotypes have been built up over generations, are “common knowledge”. You could say your personal, thoughtful experience is better (I trust my own people around me, not secondhand, thirdhand, or mass media cultural tropes—but what if I’m in an unrepresentative bubble, what if my friends, knowing the stereotypes are ashamed to fulfil them and say the opposite, in which case I should downweigh their claims and actually follow the stereotype more).
Also in adversarial settings you want to know if stereotypes are accurate data or are created with an agenda (e.g. in wartime many stereotypes about the enemy’s traits are not based on accurate understanding of the enemy; okay in a less obviously conflict-driven setting you might get this still—like stereotypes exaggerated to sell a product “get this for dad” even though your dad doesn’t fit the stereotypes, or “this city has friendly people” obviously sponsored by the tourism industry). They could be accurate however and in your best interest (e.g. the stereotype of citizens of this city being mean and unfriendly might be unflattering but your friend might generally care and tell you the stereotype (against the fear of generalizing) because if you’re stranded there, it’s good to know how much help you can expect from friendly strangers in borrowing a phone).
Sometimes there are clever things you could try, for example find out whether female chimpanzees like chocolate more than male chimpanzees… but of course there are situations where the rational answer is simply “I don’t know”.
That doesn’t necessarily mean no data, but could mean data that you strongly suspect are filtered or fake, without being able to sort out this mess. In other words, all evidence you have is very weak evidence: personal evidence may be weak because it is likely to be a result of your bubble (you are more likely to associate with people who like chocolate as much as you do), media evidence may be weak because media do not have sufficient incentives to say true things.
EDIT: Of course, saying “I don’t know” can make both sides angry that you don’t see how the stereotype of obviously true/false. Sometimes it is smarter to not say what you actually believe, even if the actual belief is “I don’t know”.