I've got two points, then I'll leave this discussion.

Point 1: In those videos the distance between aggressor and would be victim was too small, the weapon should have already been drawn. If it was unclear that the one person was soon to attack then the would be victim should have put some distance in between them. It's called being aware of your surroundings.

Point 2: What good is a defensive weapon that's not ready to go?

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Jorge