Actually, a "Big L" Libertarian does not see the role of police as protection. Police are there to enforce the law, not to proactively stop people from breaking the law; personal (self-) protection is the responsibility of the free moral agent.

It's an important distinction because if you see the role of the police and government as "protection" or "prevention", then it opens the door to all of the nonsense we have today, from smoking bans to the war on drugs.