Sparked in the comments from this entry at Bookworm Room. The original entry was about progressives trying to abolish the police, but it took an interesting turn in the comments.

Very fair. Just let me know where to go on the site. And I don't really want to make it about libertarianism. What I want is for Libertarians to prove that they can win over Democrats and Leftists within the Democratic party structure because if they can't then all they are doing is undermining everyone else and that is what I think is a fair discussion.
— RaymondJelli, post link

The simple answer is that I can't. No libertarian, small “l” or capital “L” can.

But no conservative, Republican, or social conservative can prove they can win over Democrats or “Leftists” within the Democratic party structure.

And it doesn't stop there. No “Leftist” can prove that they can win over Republicans or social conservatives or just plain conservatives in the Republican party And no “Leftist” can prove that they can win over libertarians or Libertarians.

It's a flawed question. There is no one right way that everyone must follow. There is only the temptation based on the default assumption.

Politics is adversarial because politics is controlling the Other (while preventing them from controlling you). Politics assumes that you know what is best and therefore are morally justified in deciding for the Other. Even if they disagree. Especially if they disagree. Because it's For Their Own Good. Or The Greater Good. But if you can't coerce them, you can only try to convince them. 

And for that, the only real answer is practicality. What works in real life without outside intervention? If people aren't allowed to choose except between the oh so carefully approved alternatives, is that really a choice? If they choose wrong but no one else is harmed, will they be punished? What happens when no Authority bails them out of their troubles, when they and only they are responsible for the consequences of their own words and actions? 

What happens when you can't depend on government to make it right by force if necessary?