His father was one whom a mote in his brother's eye repelled.
I suggest that the beam in our eye is simply our unloving reaction to the other man's mote.
"There's a mote in't," quo' the man when he swallowed the dishclout.
When only apparently a mote is found, it is exaggerated to a very great beam.
At that time Ruth had been less than a mote 28 in the eye of Uncle Jabez.