I may own a gun, but can I point it at you, thereby threaten you? No. Prostitution and drugs are an endangerment to my being, my property value, my children's welfare, and my community's quality.
Only if you lack the character and self-restrain to refrain from drug abuse or promiscuous sexuality.
I guess if you fear that you are unable to control yourself, the next best thing is to ask government to do it for you.
What you have described is the direct threat of initiation of force, and it would directly violate libertarian philosophy. Funny you should use that as an example though, because that's precisely the means used to prevent the voluntary act of prostitution.
Prostitution and drugs are an endangerment to my being
How?
my property value
Only because it's illegal and driven outdoors. In places where it is legal, it is centralized in certain areas, away from homes and churches. This is like any other business, say an oil refinery locating in your neighborhood. BTW, you have no right to high property values at the expense of your neighbor's property rights.
my children's welfare
How? Your children's welfare is your own responsibility. This isn't Hillary's 'village'.
and my community's quality
Communities have no rights, only individuals do.
Apples and oranges. In a libertarian (or any) system of laws, your first example is clear-cut evidence of criminal threat. Your second example (prostitutes and drugs) would be prima facie evidence of no crime in a libertarian system---you have to define these behaviors as criminial in order to make them criminal. You're assuming that prostitution and drugs---however broadly you define them---necessarily create crime. In other words, you're not fighting the actual crimes you fear, like stick-ups or drive-bys or what have you, you're railing against what you perceive is the cause of the crime.Why create bad law? Fight actual crime---a stick-up is a stick up whether or not the goal was to score money for crack or baby food.
Using the same justification, I could say that your owning an SUV degrades my environment (emmissions), endangers my children (via size-of-vehicle in accident) and destroys my communities value (offroad driving).
Also, if prostitution endangers you, then so does extramarital sex and unprotected sex or ANY sex in general (via neccessity of welfare for children).
The reason we let you have a gun is to allow others to enjoy freedoms that, yes, maybe-might-could, endanger you [just like alcohol use, or you having a gun in the first place]. (The real reason drug use endangers you is your insisting on its illegality, creating the black market and drug-related crime).
Act like a sovereign, not like a cowering thumbsucker.