The only stance on the life issue that ever succeeded in uniting people in the liberty movement was the stance of Ron Paul. Johnson's (personally) pro-choice stance guarantees that he will never function as a uniter, and will always be a divider.
Johnson's pro choice stance would probably prevent me from ever donating money to him, but if I were living in New Mexico I would probably reluctantly vote for him. He does support overturning Roe v. Wade and opposes all federal funding for abortion, so his actual policies on the abortion issue aren't nearly as bad as someone like Barbara Boxer.