What the research found, including where it is thin
Two studies. The first separates the two states and shows they predict opposite things. The second is the strongest single claim in this course, and we are printing its limits next to it rather than after it.
What the research says
Dearing RL, Stuewig J, Tangney JP (2005). On the importance of distinguishing shame from guilt: Relations to problematic alcohol and drug use. Addictive Behaviors, 30(7), 1392 to 1404 doi
Shame and guilt can be measured separately and they go in opposite directions. A tendency towards shame, which is feeling bad about the self, went with more problematic alcohol and drug use. A tendency towards guilt, which is feeling bad about the act, did not, and if anything went the other way. Feeling worse about yourself is not a route to doing less.
Randles D, Tracy JL (2013). Nonverbal Displays of Shame Predict Relapse and Declining Health in Recovering Alcoholics. Clinical Psychological Science, 1(2), 149 to 155 doi
Shame shown in the body and the face, coded at one point in time, predicted relapse and worse health later on. The limits, and they matter: this was in people recovering from alcohol dependence, not in anybody using pornography, and the sample was small. Read it as evidence about shame and relapse in general, which is what it is, and not as evidence about this behaviour in particular.