Abortion at any level is indefensible if one is a true Libertarian. Liberty is defined as freedom from opression... there is nothing more opressive than denying an innocent human being of its fundamental and inalienable right to life... let alone try to argue one's "liberty" gives them the right to.
This is a complete bastardization of the very concept of Liberty. Until the libertarian party can face the truth on abortion, its nothing more than a bunch of recreational drug users looking for justification for their self destructive ways.