Or for a better example of a perfectly above-board and healthy activity enjoyed by huge numbers of people that can become addictive and "a problem" - how about gaming?
(I'm not trying to belittle your point or resort to "whataboutism" here, just pointing out some examples from other industries).
The problem with porn is that it's sex and sex is dirty and bad and you should feel ashamed for having anything to do with it. /s
So yeah, like you, I'm not buying the entire "because some people are addicted" angle either. We are sold addictive substances all the time.