That is what a conservative libertarian would say. ''Protect the liberty of a certain group of people, for example the american people. This is how the greek athenian democracy worked as well. It was a democracy for men. But if we start thinking about liberty to a set of people we end up with the conclusion that everyone is a libertarian (take as a set only yourself ). That would make the use of the word libertarian unnecessary (as we all are libertarians). Since the word is used to differentiate between people, we end up through Reductio ad absurdum that your defintion of libertarian is wrong.
We also end up with the conclusion that you are not a libertarian.
As a personal remark, I would say that such a wrong definition of libertarian was always used as an excuse to diminish the liberties of others.
(reading math.. right now)
--
Sincerely yours,
Apostolis Xekoukoulotakis