Mosiah 10:17

17 And thus they have taught their children that they should hate them, and that they should murder them, and that they should rob and plunder them, and do all they could to destroy them; therefore they have an eternal hatred towards the children of Nephi.

I don't understand how common sense didn't prevail in recognizing that the distant descendants of Nephi (many hundred years have passed!) did not personally harm them and didn't deserve to be hated and killed?!

How could that thought not have surfaced and made sense?

Can the lack of the spirit suck out common sense? If that's the case, can an increase of the Spirit increase an awareness of things as they really are? Provide clarity?

Yes.

Lack of Spirit=foggy mists of darkness. Spirit= Urim and Thummim, clarity, truth.

I want that, and to share it with those who are groping for a hand hold.