You are totally illogical.
Zimmerman didn’t accuse Martin of bashing his own hands on the walk, it was Zimmerman’s head that should be bruised, not Martin’s knuckles. Martin was hitting soft flesh (nose) and holding Zimmerman’s head like a ball as he bashed it on the walk.
Mortician’s findings fully corroborate Zimmerman’s testimony, and that of the eye witness.
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Agreed, the injuries Zimmerman reportedly suffered do not require abrasions on the person who may be responsible for the reasons you described.