I meant the latter, and Bernie is a member of one of the two major national parties, and did have a decent shot at winning the primary. I'm also not talking about the Libertarian Party per se, but of the small L libertarian philosophy in general. The social policy side is largely in agreement with the Green Party, and with Bernie.
This is a bogus myth that needs to stop being repeated.
The Libertarian Party platform and libertarian ideology isn't
supportive of *select* liberal social causes. It simply doesn't give a shit. In some instances, this has the same end result - gay marriage and legal weed, yay!
This runs into problems when you start talking about repealing things like the Civil Rights Act, or the Americans with Disabilities Act or other legislation designed to protect vulnerable members of society. Sure, you can be gay, or trans, or black, or a woman, or disabled, but don't expect the government to help you out. All you can do is pray to the invisible hand that local businesses decide it's better for their bottom line to have your business even if that comes as an inconvenience to themselves.
Many libertarians also support leaving these matters up to the states. Boy, that sure sucks if you live in a deep red state that can barely come to grips with recognizing you as a person! Live free or die!
Also, do you see healthcare, education, poverty etc. as social issues or economic issues? Because I'd say they overlap strongly and those are certainly not points in which the Libertarians and liberals are generally in agreement.
Don't try and sell libertarians as a perfect combination of social liberal + fiscal conservative. It's an ideology unto itself that barely overlaps with liberalism and any Bernie supporter going to Johnson is either a moron or a one-issue voter (but I repeat myself).