Your double "supposes" are a bit redundant; if someone arrives at a belief other than through evaluating the evidence, they chose it because it is "satisfying in some way".
... or because they got confused (took it as a supposition and forgot that was its role), or have never really considered the issue carefully and gone with the first thing their intuition suggests, or...
It's not redundant. Stretching the first to encompass the second is too much stretching.
Sometimes I run into people that have rather strong opinions on some topic, and it turns out that they are basing them on quite shallow and biased information. They are aware that their knowledge is quite limited compared to mine, and they admit that they don't want to put in the effort needed to learn enough to level the field.
But that's not really a problem. What is bothering me is that, sometimes, that declaration of ignorance is expressed with some kind of pride.
This behaviour is noticeable on other levels too, in politics or in the sciences-humanities culture clash.
I came up with several hypotheses which might account for this:
Do you notice this behaviour too? What do you think causes it?
EDIT: formatting, style, grammar