The author has reversed the cause and effect. "Sex addiction" is not the cause of immoral behavior, but the effect (result) of yielding to the sin impulse that is inherent in everyone since the Fall in Eden. Sin is the root problem - not "sex addiction."
The plethora of "addictions" today is merely man's latest attempt to thwart personal responsibility, a tendency that began in Eden (Gen 3:11-12). Until one recognizes and acknowledges the truth of inherited sin as the starting point, they are defenseless in the battle. And there is only one Power in the cosmos that can free us from sin's universal and deadly influence.
If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. (1 John 1:9, ESV)