Generally speaking, a belief has value to me when incorporating it into my world view makes my reality more plausible, more workable.
Then again, my reality itself is already shaped by core beliefs (which I am possibly not even aware of).
IOW I have an inner map (my reality) that guides me through life, and has done so for decades in a sufficiently reliable way. Sometimes - with additional insights - I have to make minor changes to this map, sometimes the required changes are more thorough (and can be quite painful in that they require me to acknowledge that a lot paths I went - based on this map - were pointless, etc.).
Worst case scenario: Incoming information would require me to consider my map entirely worthless, to throw it in the dust bin altogether. This is a very threatening scenario, because it would leave me without any guidance, without any orientation; my entire system would break down.
This is probably the scenario in which I´d likely counter every argument by pointing to my inner map ("common sense", "everyone knows", "it is self-evident, that..." or something to that effect). Of course, I would not be aware of what I am doing.
Chances are that accepting the argument of the other poster would have made his inner map useless (or that he sensed that the implications following from accepting the argument would eventually threaten the worth of his inner map).
Well, (objective) "reality" is a very delicate concept to operate with.
We usually don´t have problems with accepting information of the "objective kind" (i.e. raw data, if you will), simply because they are meaningless (until we interprete them, relate to them, give them meaning or significance or derive implications from them - at which point they have ceased to be objective raw data).
And another thing: Even though his behaviour points to the fact that his inner map was directly or indirectly threatened, concluding that therefore the belief he held was "contrary to reality" is rashed: there may well be rational arguments for his position - he may just not have known them.
Indeed - it allows for the conclusion that the worth and usefulness of his map was threatened to a degree that struck him as intolerably destructive to his system.
It does
not, though, allow for the conclusion that his system is wrong and the rejected information was correct.
That´s what I have tried to explain above.
So you yourself have such a belief that is so essential to your thinking and has shaped your inner map so thoroughly you´d defend it at all costs. Can´t you extrapolate from there?
I think the beliefs that have shaped my inner map (and abandoning which would therefore threaten my entire system) are not of the kind that can be threatened by objective information. Which seems to be the case with all beliefs that fall more on the metaphysical side.
It seems to me that your core belief ("truth allows me to make better choices, better decisions, and is a better guide in my life than falsehoods") is of that kind, as well. It protects itself against being threatened by objective information or raw data by virtue of employing subjective keywords ("better", "better guide").