I'd still say that by changing your activities, you can redirect or train your thoughts, but you are still never able to control them. But that's just all semantics. I get what you're saying. What we are both saying is that you can control your actions (whether to watch porn or not, for example).
I am just very wary of focusing too much on policing what your partner is thinking (and that includes expecting them to go to great lengths to attempt to control or retrain their own thoughts). It seems a fruitless, and possibly cruel, exercise, and one that doesn't seem sustainable for a good 50 years of partnership--if that's what you're aiming for.
The very concept that your partner has different thoughts from yours, and unexpected ones, is hopefully the most delightful thing about them.
Both me and my husband have changed our minds about things in our years together in a slow, lovely process of respectfully discussing things and listening to each other, and then thinking about what the other said. That's the way thought processes should evolve: with lots of room to roam about the head without shame.
I realize this is a slight thread derail by now, because our original issue is: is porn cool or not? But I hope this is at least related.