I think most of us are so sure about so many things.
In the West (or in any country and culture strongly influenced or rather contaminated/polluted/infected by the disease like nature of Monotheism), I think it’s natural for people to be over simplistic and too sure of many things because Monotheism simplifies things/matters down to single (imaginary) source they call god. All fine and/or difficult questions are avoided and settled using the “omni-XXX”, ”absolute/infinite-XXX” nature of god, too easily.
So, people are mentally conditioned to see and think about things in overly simplified and definitive manner rather than careful and prudent approach that tries to maintain precision and finer distinctions.
As result, people tend to think and talk in definitive and over assertive manner regardless of their (often very shallow) level of understanding. especially in monotheistic culture (although other culture may share the tendency to different degree).
It’s more so when people are religious. What they say can be often very illogical and incoherent and practically meaningless (other than the expression of subconscious hope and fear), to my personal taste.
It is interesting to note that most people think to obtain more certainty but end up in settling with substitute certainty called belief or rough theories/hypothesis as if they were absolute certainty.
However, although it’s rather rare, there are some people who care about the quality of the certainty they seek, and usually they end up loosing the substitute certainty and/or overrated certainty they had by cultural, biological, and other conditioning. And they become less certain about many matters, and they may even start seeing the potential result of seeking certainty with precision, which is the general lack of any definitive certainty or the lack of any absolute certainty in any matter.
They learn that they don’t know much, and possibly not at all with absolute certainty and become whole a lot more prudent in expressing something definitive.
It can be seen as ironical that people who seek the certainty with more rigor would end up in general uncertainty, often loosing all the certainty they thought they had.
Strangely, if the exercise of seeking the certainty is done with enough rigor and care, the resulting uncertainty would be so undeniable that the negative effects and uneasiness caused by the uncertainty can be minimal or non-existent.
I t seems we get uneasy with the uncertainty when we think/hope that we can find (quick and easy) certainty somewhere and look for it, left and right. But it (uncertainty) does not produce much uneasiness when our regard is fixed on it and when we don’t wobble nor swing our gaze/focus.
In other words, the uneasiness associated with uncertainty might be coming from the hoping and seeking the quick and easy (substitute) certainty and the resulting unsettled/wobbling focus.
The wobbling/unsettled focus might well be the source of uneasiness, and that’s possibly why even the cheap substitute like religion and god can provide some level of relief because they settle the attention to some degree.
However, the cheap and substitute certainties aren’t well examined and thus people clinging on them know the low reliability of them (usually subconsciously), although they may try to boost their certainty scale by repeated affirming words like “real”, “fact”, “true”, “exist” and/or by worshiping, glorifying, and overrating them.
And the (subconscious) knowledge of the fragility of their certainty may make them uneasy and even fearful and then sometime angry when something/someone remind them what they claim to be certain isn’t that sure.
I think this is why anyone who holds onto fake certainties, fake absolutes react often badly in conversations and in discussion forum like this.
And it is applicable not only to simplistic religious people but to atheist, materialist, and anyone who pretend to be sure of something more than they actually can be.
Having said this, settling with the easy and unexamined conclusion that thing are unknowable or uncertain would not do much good. It’s similar to adopting cheap and quick position declaring “I’m an idealist (or materialist, humanist, nihilist, etc)”. Unless the gaze into uncertainty resulted from honest and rigorous quest for the certainty, our desire for the certainty remain intact and the wobbling/swaying tendency of our regard/focus to look for the certainty would stay unchanged.
So, if we want to be sure (and I think it’s our natural tendency built into our logical mind to desire the certainty), we’d better seek the certainty with the utmost rigor and precision we can think of, even if it might (and it’s likely to) end up in general uncertainty when it’s done, well enough.
In other words, from my preferred point of view, the sign of superficial certainty (especially of unlimited and/or generic nature) indicates that the person have most probably caved in to the desire to have ANY certainty and it’s likely to be not very reliable nor meaningful.