Beliefs come first; reasons second.
We humans flatter ourselves when we claim to "think" things through, because often our starting point is our conclusion. We rationalize our conclusions and biases, and are attracted to information which confirms them. However, that does not mean that our thoughts are always misguided or wrong.
Our New Hampshire friend has recently discussed the topic:
Anyone who does not know why they hold a particular viewpoint cannot judge fairly whether it should be kept or abandoned. There’s no point in arguing with them.
That's the point. It is in fact a Psychoanalytic point. Two good rules of thumb for introspectives are these: "Don't believe everything you think," and the old AA aphorism, "Feelings aren't facts."