The following is a personal perspective... an opinion if you will...
I am not a sheep for I do not mill around with the flock with my attention on fitting in with the flock.
I am not a wolf for I do not prey on the sheep.
I am not a sheepdog for I do not have the responsibility or desire to control or protect the sheep... nor do I have any wish to fight the wolf.
The word "wolf" is an accurate term for predatory criminals so I have no problem with that term.
I am a stray dog... I am warily friendly to the sheep and I avoid the wolf as I fend for myself yet I will fiercely fight to protect those I love... from both wolf and sheep.
That said... I don't like using the word "sheep" because it is derogatory to people who need to be educated that they too can defend themselves from the "wolf".
And the word "sheepdog" sounds so noble and nice... to be someone who protects the weak and innocent... but honestly look at what a "sheepdog" actually does with the "sheep" entrusted to it... it is the "sheepdogs" job to control the sheep in return for the illusion of the flock being protected while the dog's master does other, more important, things.
My job is to maintain control of my own ability to protect myself and those I care about... and in order to do that I carry a gun. I might come to the aid of an innocent person because my morals and ethics require helping those in danger but carrying a gun does not make it my job to help others... therefor as a private citizen I am not now, never have been, and never will be a "sheepdog".