Well there is a difference between anarchy and libertarianism. I think SPC is more of an anarcho-capitalists than a libertarian though. Anarchy = no government and no respect for rights of others. Anarcho capitalism = no government, but respect for rights of others. Libertarianism = minimal amount of government to protect rights.
Well, anarcho-capitalism is a smaller branch of libertarianism. The dominant minarchist branch believes in minimal government to protect rights, though I'm skeptical of how that could work in practice, given that every government has a tendency to expand beyond its "limits".
Because we elect Republicrats instead of people who care about the constitution. With the right people (such as Ron Paul), government won't expand. We just need to stop putting the wrong people in, which is easier said than done.
I'm skeptical when the Republicrats give us McCain and Obama and tell us we are free because we get to pick one of them.
One of my many problems with liberitarians is that they often put Democrats and Republicans in the same categories. That is just stupid, we have clear and obvious differences. Statism is not an ideology.
So? From our point of view, your differences are pointless. It's like someone telling you that there are clear & obvious differences between fascists & monarchists. From your point of view, both are extremely undesirable & must be opposed at all costs.
I'm not one to talk though since I, from time to time, support candidates from either party in order to prevent their opponent from winning, but eh.