See, this tendency of libertarians to reduce every political question to a discussion of who's allowed to shoot whom is exactly what holds them back from being able to participate usefully in politics. There's far more to organizing a society than that.
Even within the examples you give, though... the difference between the anti-gun leftist and the anti-abortion rightist still is basically a question of who gets to use violence against whom. They're both fundamentally advocating the defensive use of force, which libertarians are generally okay with—the leftist wants to use violence in order to reduce the risk of someone else doing violence using a gun; the rightist wants to use violence to defend an unborn baby from the violence being done against it by a doctor. The disagreement between them comes down to deciding what constitutes violence or the threat of violence sufficient to justify the use of violence to prevent it. So even within a political framework based entirely around the question of violence, you can't handwave this particular left-versus-right question away so easily as that.