One must be careful.  For instance, in the scenario the man in the video described, he unholstered and pointed his weapon at at least one of the men before any of the men physically assaulted, brandished their own weapons, or did anything which would have objectively put the man in the video in immediate fear of grave bodily harm.  Now, depending on which State this scenario occurs, there could have been a variety of different legal outcomes.  For example, in the State in which I reside, if I had acted in this manner under the same circumstance, I could have been charged with a crime, because there mere act of unholstering a pistol and pointing it in in a general direction is considered the use of a deadly weapon, which can happen only after I am objectively in a state of fear of my--or others in my immediate vicinity--immediate and grave bodily harm.  The acts of the vagrants in this scenario would not have risen to that level.  Now, does that mean I agree with that, and more importantly, disagree with the actions this man took to ward off an obvious threat?  Of course not.  But unfortunately, the laws in many States are not written in your favor, but instead in the favor of criminals.  

Just something to think about. Or rather, know the laws of your State, and understand that said laws can, and do, change from State to State.