How is the evidence the evidence? I don't know how to respond to this?
It boils down to prejudice. Had this been a citizen defending themselves there are many who would take their statements at face value and consider it done. Since it was LE there are some willing to take their statements as fact and consider it done. Between the two you will find the law which is designed to exclude prejudice in favor of truth and justice. May not be perfect but it's what we've got and I've not seen a better alternative.