Watching porn is just the symptom of a bigger issue; breaking of the 1st, 7th and 10th commands. Take away the end result and one does not need a means:
28 But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart. 29 And if thy right eye offend thee, pluck it out, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell. 30 And if thy right hand offend thee, cut it off, and cast it from thee: for it is profitable for thee that one of thy members should perish, and not that thy whole body should be cast into hell.
The Holy Bible: King James Version, Electronic Edition of the 1900 Authorized Version. (Bellingham, WA: Logos Research Systems, Inc., 2009), Mt 5:28–30.