Horses are a
symbol of
masculinity for various
reasons, including the
image of the
knight on his
steed, much beloved of
fantasy and
romance novels.
Obsession with
horses (as well as
unicorns and other
variants) is a common
phenomenon among
pubescent girls who are also beginning to be
sexually
interested in
boys and
men.
Some say that the real reason for all this horsefulness in Western romance is that stallions have big penises.