This isn't a no true Scotsman fallacy, because parties do have official, stated platforms. And to my knowledge, this is not part of the Libertarian party platform.

Being able to find some members of the party who support an idea is not the same as saying that "many members" support it. And frankly, I'd be very skeptical of the notion that this idea has widespread support within the Libertarian party, given the rest of their platform and values.

~"If two libertarians ever find themselves in agreement on a particular issue, they know that one of them has sold out."