Most libertarians are
Mandated national service on the idea that you as an individual “owe” something to society is a perfect example of the Left thinking the State has superiority over the individual. To them there is no concept of natural rights. To them all rights are bestowed by the State and you “owe” the State.
Rand is right. You are not born “owing” the State. The State has no claim on your rights. They are yours inherently.