In The Pigman, why do you think John defended Lorraine when Norton called her a screech owl?

There are two reasons.  First, he doesn't like Norton.
Norton is always making fun of people.  Lorraine is John's best friend, so it angers
John and he gets defensive.  He calls Norton names is return to give him a taste of his
own medicine and make him think twice about disrespecting her
again.

To go even deeper though, John seems like he has
even deeper feelings for Lorraine beyond friendship.  Their friendship is a curious one
to begin with since they are such opposites, but when they spend time at the Pigman's
house, the reader can see a romantic relationship being formed.  Of course, the kiss is
the obvious example of this, but the way they interact afterwards, John's bossing her
around and their bickering back and forth like husband and wife, shows the reader he
cares for her on another level which is why he felt he had to stand up for her against
Norton.