I'm sure they think they are. That's part of the problem, the other part of the problem is that they don't know thats none of their business. A well meaning tyrant is still a tyrant.
I can come up with a whole laundry list of things that "would be best" for other people, and if they were made law, people might be a whole lot better off in some ways, such as wealth, efficiency of time, finances, life span, etc..., but they would be a lot worse off in terms of freedom.
It is not the proper role of government in a free society for government to play mommy and engage in social engineering, and the fed violates its constitutional charter by blackmailing states to enforce its drinking age.