And who's to say I'm not armed? I didn't "look" armed? Or in retrospect, after you've shot me and sent by buddies running, you can look back and say "well, gee, I didn't really think he was armed"? That's the thing about trying to analyze what we know happend with what might have happened.
We KNOW the young men were chasing the son (no one denied that). We KNOW the young men harbored racial hatred (I'm no fan of so-called hate crimes, but it does speak to motive for attempted assault or murder). We KNOW the young men didn't disperse, even after dad came outside to scare them off.