I think I know where you're coming from. And it's the semantic difference between the theoretical or ideal libertarianism (with the small "L") and true libertarian politics under the Bush's, the Clinton's and now Obama. Search: "8 ways Ronald Reagan was a libertarian" for a good explanation of why and how he truly embraced libertarianism. The three legs of the Reagan Revolution were, after all, "privatization, outsourcing and deregulation."
Reagan said, "I believe the heart and soul of conservatism is libertarianism." He said, "As government expands, liberty contracts." Also, "Government is not the solution to our problems, it is the problem."
He was definitely a "corporatist," and the "smaller government" he wanted still had a huge military budget, including a classified black ops budget in Central and South American and support for the Contras in the U.S. proxy war against the Nicaraguan Sandinista government.
A libertarian idealist would be a non-interventionist when it comes to foreign policy, almost "anti-war." They would also abolish the failed War on Drugs and decriminalize drug use to eliminate the state's involvement in propping up a huge black market and a system of citizen surveillance which has continued to expand under the pretense of the War on Terror.
So Reagan and every other president since him cherry pick those libertarian ideals that best serve corporate America and ignored those which would have interfered with the "free market" in things like military arms sales, "guns for drugs" and private prisons - the very things that libertarian idealists despised for their negative impacts on life, liberty and human rights. In that sense, Reagan was not a "good libertarian" but one of the very worst.