The thing is that someone like Aguila Blanca (or me, for that matter) would be able to articulate why a reasonable and prudent person in like circumstances (i. e., a geezer like us) could reasonably conclude that an unarmed attacked by someone clearly younger and stronger could kill or gravely injury us. That's called disparity of force.
On the other hand, claiming justified use of lethal force against one or more unarmed assailants on a disparity of force theory can be an uphill fight. While
Larry Hickey, Mark Abshire and Gerald Ung were ultimately able to prevail in their legal battles, they didn't have easy times of it.
Perhaps Mr. Gutmarcher explains it all a little more artfully and in greater depth than it's been paraphrased.