It's a matter of akrasia—if we can decide what makes us happy, then that implies that there's some sort of "meta-happiness"—a utility function that will be "best" maximized compared to other ones. Some people think that a utility function that doesn't include enjoying porn is better than one that does.<p>Of course, this is all theoretical if you can't change what makes you happy—and, since psychological studies say that <i>how much</i> you can change your utility function is something that varies individual-to-individual, there will never be a widely-accepted belief that it's impossible to decide what you like, as there will always be <i>some</i> people who can.