I think part of the problem is that most people are conditioned into many beliefs from a young age
I know a guy who hates foo (using a place holder). In fact he's downright foophobic. He is pretty convinced he has a natural unbiased hate of foo and is being rational when he expresses it.
To me as an outsider it is pretty obvious that his hate of foo is the result of cultural conditioning. To him it is perfectly rational to hate foo and to me it is totally irrational, especially since he can't give any concrete reason for it.
It could be a case of implicit vs explicit knowledge. In the context of evolved culture beliefs, the foophobia may serve some real purpose, even if most/all of the enculturated individuals can't explicitly state what the real purpose is.
It could be that, like dietary restrictions to reduce the spread of disease, the foophobia is no longer needed, but keep Chesterton's fence in mind before you say it's unneeded.
It really depends what foo is. I don't think it's rational to waste time on unimportant things. If foo is eating red meat, then I don't think it's rational to really worry about it one way or another.
I think part of the problem is that most people are conditioned into many beliefs from a young age
I think it's irrational to not consider new information when processed. So, again, this depends on what foo is. If it is obeying speed limits even when no one else is on the road, and your friend learns the penalties for not obeying road signs when they get their license, they would probably find it irrational to not do the speed limit, even if they hate it. They wouldn't want to risk the fines, license suspension, etc.
However, let's say your friend's brother has stronger beliefs and can afford any fines and legal action. He could think about it and still decide that it's rational to not obey the speed limit. This doesn't make it right; I think right and rational are mutually exclusive.
When I mention conditioning, I mean from a very young age.
For example: Throw salt over your shoulder if you spill some -or- Green skinned people are bad and you should never trust them or allow them in your neighborhood.
Now the former is pretty harmless but not so the latter. In both cases the only explanation is "that's how I was raised" which I don't find compelling or rational.
If the person has some stronger belief (e.g. people are important, and hurting them unnecessarily is bad) that can override “never allow green-skinned people in your neighbourhood”, they're redeemable. If they don't, they're evil. (Evil people can be rational, too.)
Value judgements exist in a separate domain than pure rationality.
I like chocolate ice cream more than vanilla ice cream, and you're not gonna convince me otherwise by debating the flavor with me. It entirely could be the case that my preference is from cultural conditioning, but it's not my concern.
If your friend has a mindset of "to each his own" there's no problem.
> to me it is totally irrational, especially since he can't give any concrete reason for it.
In my experience, people usually can give ‘concrete’ reasons for it, but what constitutes ‘concrete’ is a matter of opinion, and I don’t consider everybody’s reasons to be valid. But of course, they do.
I know a guy who hates foo (using a place holder). In fact he's downright foophobic. He is pretty convinced he has a natural unbiased hate of foo and is being rational when he expresses it.
To me as an outsider it is pretty obvious that his hate of foo is the result of cultural conditioning. To him it is perfectly rational to hate foo and to me it is totally irrational, especially since he can't give any concrete reason for it.
So who is right and who is being rational?