Why does Tom Weylin whip Dana in Kindred by Octavia E. Butler?

In the novel
, bywe meet Dana and Kevin Franklin.  They are an interracial couple who
are moving into a new home.  Dana is taken suddenly back in time to the Civil War era and being
an African American this puts her in danger.  She is called back each time Rufus Weylin is in
mortal danger and she saves his life over and over. 

On one trip back in time
Rufus is drowning, another time he is setting the house on fire, and one time his leg is broken
from falling out of a tree.  It is during this incident that Kevin, Dana's white husband, grabs
on to her and returns to the old South with his wife.  During this visit Mr. Weylin discovers
that Dana can read.  He tells her he will permit her to read to Rufus but not to read anywhere
else and not to touch his books.  She chose to teach one of the slave children, Nigel a
young slave boy belonging to the Weylins, who is the same age as Rufus.  She is leaving the
cookhouse with a book and is discovered by Weylin. He whips her for disobeying him and taking
the book.

Later she is whipped for trying to escape.

"After being beaten following her attempt to run away, however,
Dana is tormented by doubts about her own resistance: "Why was I so frightened
nowfrightened sick at the thought that sooner or later, I would have to run again? €¦ I tried to
get away from my thoughts, but they still came. See how easily slaves are
made? they said."