In deciding whether exposure and response prevention (ERP) makes sense for this client my first question is "Are we dealing with OCD, a paraphelia, Obsessive-Compulsive Personality Disorder, or someone with rather extreme religious beliefs?" ERP is likely to be promising if the problem is OCD but I'm not sure it would apply with the other possibilities.

This case is not simple diagnostically. The client's fear of thinking sinful thoughts and avoiding stimuli that might trigger sinful thoughts certainly could be OCD. However, his pattern of channel-surfing until he finds something provocative then masturbating, then surfing more, then masturbating more, etc. sounds like a paraphelia, not like OCD.

I'd want to develop a detailed understanding of the sequence of events and the client's affective response to the thoughts and fantasies he experiences. Then I'd pull out DSM-IV and make sure I'm remembering the diagnostic criteria correctly. If the sexual thoughts/fantasies that he experiences are consistently aversive and are experienced as intrusive, unwanted thoughts that he cannot get rid of, then this might be OCD, especially if he has a history of more typical obsessions or compulsions or a family history of OCD.

However, from what you've written it sounds as though the sexual thoughts and fantasies are pleasurable at first (until he starts feeling guilty over having "sinful" thoughts) and it sounds as though he sometimes seeks out the sexual thoughts and fantasies rather than always avoiding them. If so, this doesn't sound like OCD, it sounds as though either (1) he has ordinary sexual thoughts and fantasies but feel excessive guilt over them or (2) he has a paraphelia (possibly voyeurism). If the problem is excessive guilt over ordinary behavior or is a paraphelia, then ERP is less likely to be appropriate.

When you have time, fill us in on this (changing any potentially identifying information, of course) and I'll have more comments.

Note: I generally wouldn't have a compulsive gambler stand outside a casino (after all, compulsive gambling isn't OCD). However, I can think of scenarios where it might be a good idea. For example, suppose a client with a compulsive gambling problem lives in a town with casinos and it isn't practical for him to simply avoid passing casinos. Late in treatment when working on relapse-prevention it might be quite useful to use ERP as part of the process of equipping him to resist temptation. However, it would need to be done carefully because of the risk of triggering a relapse.