Private security, since it offers the advantages of labor specialization, economies of scale, and immediately-available on-site services, is a much more practical and realistic response to violent crime than the alternatives.
In Ron Paul’s America, or Hans Hoppe’s private law society, voluntary “socialist” arrangements would be perfectly allowable and legal. But libertarian communities are never permitted in statist societies.
If allowing markets to operate represents an "ideology" to most people, so be it. I would argue that markets represent a lack of ideology. More importantly, markets provide far and away the most practical approaches to difficult problems like terrorism.