... you are on thin ice with this "hormonal" driver and "freak of nature" explanation unless you are willing to conjure a similar way to explain pedophiles, necrophiles, etc., etc. throughout the realm of aberrant sexual behavior. Some people do make strange choices with their lives.
And, interestingly enough, all of those behaviors along with homosexual behavior, addictions, and other compulsive disorders are extremely difficult to change. To the point that some argue they are impossible to change.
