Well that's not really a full picture if you take into account that we live in a society... Everyone's actions have externalities, living in a liberal culture is a very different experience for a conservative than for that same person living in a conservative culture, their communities will be very different and affected by the larger culture, etc etc etc. Yours is a very liberal/individualistic point of view. Which is fine but there are plenty of other points of view.

That's the social liberal version of the "rational economic person” fallacy. It assumes that people know what will make them happy, and that people--especially young people with developing brains--can work toward those ends without education and social reinforcement.

In reality, most people don't know what choices will make them happy. How could they? And even if they did, they wouldn't know how to get from Point A to Point B, or have the willpower and discipline to stick to it. They need society to develop generational knowledge about those things, socialize children and young people to understand that learning, and socially reinforce good choices. And frankly liberals know that because in other respects, they support societal intervention to protect people from bad choices and help them make good ones. They just have this huge blind spot. The act like the young adult who needs society to protect them from predatory lenders doesn’t need protection from people who might exploit them in other ways. Or that the person who needs education and social pressure when it comes to sugary soft drinks doesn’t need it when it comes to far more impactful decisions about how to live.

And that's before we get to externalities. That's another concept liberals understand but pretend has no application to social norms and behaviors. As if divorce or drug use only affect the individual and not people around them.

You assume incompatible axioms. If everyone can live however they want, then oppression would be impossible if they don't want it.