Because only the ACLU seems to come close to pushing various vices like the Libertarian does.
Ever occur to you that our Constitution protects liberty by ignoring what bluenoses like to call 'vice'?
-- Get over the idea that you have the power to control your neighbors 'sins', guy.. -- You never have - and you never will. Not in the USA.
Let me school you, grasshopper...there is a huge difference between advocating an action and permitting an action.
I won't encourage you to fullfill all your lurid fantasies but as long as you are with consenting adults in private I won't interfere or encourage government interferenece.
I don't have to advocate gambling to 'allow' others to gamble; I don't have to advocate tobacco or recreational drug use to 'allow' others to do so; I don't have to 'advocate' porn to allow you to look at it; and I don't advocate idiotic opinions yet feel no complelling need to stop yours.
The LP does not "push" pornography, drug use, homosexuality, abortion, prostitution, or any other vice even though you falsely claim that is does.
Me? I don't feel the need to use the state to protect people from themselves and to prevent them from doing things that I don't like.
You do.