Look, it’s not that hard.

The following things can both be true at once:

(1) People are different.  They have different needs from each other.  Any standardized model of the Good Life will be toxically horrible for some people, no matter what that model is.  For that matter, a life model that you find disgusting and awful is probably Exactly Perfect for some people.  Even if you really need X, even if you think most people need X, some people need Y instead. 

(2) People are not always good at understanding their own needs.  Sometimes they want things that are bad for them.  In particular, it often happens that some particular thing is widely desired but actually harmful in the modal case, because for some reason it’s “more attractive than it should be.”  (Maybe it offers short-term rewards for steep long-term costs, screwing with common introspective failures relating to time.  Maybe it offers a slim chance at fabulous payouts, screwing with common cognitive failures relating to probability.  Maybe it plugs into some widely-valorized social narrative, in a way that disguises its real ongoing costs.)  Sometimes it’s the case that most people really do need X, only a very few strange people need Y, but nonetheless there are many who will end up choosing Y over X if they have the autonomy to do so. 

In such cases, there are concrete dangers to the pure liberal stance; autonomous people acting freely are likely to hurt themselves.  You can end up concluding that the costs of liberty outweigh the costs of paternalism, or vice versa, but it’s an actual tradeoff.