Someone pointing a cellphone in your face, even acting belligerently doesn't meet the standard of fearing for your life.
People that scared of the world shouldn't own guns.
Youtuber was definitely as asshole and he definitely had something coming to him but you can't just shoot someone who's annoying you and putting a camera in your face.
I see in another comment you deride first year law classes. Mind if I ask what year you're in?