Mixed inferences & Meta-metamaphoricity

What does this mean- 'Let he is who is without sin cast the first stone'?
The context is the homely Hebrew custom of stoning adulterers to death.
If St. Paul had made this statement it would read as an example of mixed imperative inference and the meaning would be 'Don't stone adulterers. The only righteous stoning of a sinner occurs where the first stone is flung by Lord Jesus Christ himself.' This is because St. Paul is a sinner just as we are, for in  Adam's Fall, we sinned all, only Lord Jesus Christ being free from Original Sin.
What, logically, is the meaning, from the point of view of an orthodox Christian, of attributing this statement to Lord Jesus Christ?
His statement permits stone throwing but asserts his own right to throw the first stone in the same manner as the President has the right to the ceremonial first pitch in American baseball.
However, Christ did not in fact throw a stone. Thus we know that though it would have been permissible for him to throw the first stone, it was not obligatory for him to do so. But, Christian orthodoxy does not consider that there were any obligation arising from Jewish law that it was incumbent upon Christ to follow. Nor was it incumbent upon him to conform to later Christian Canon Law. Thus, from the fact that Christ did not actually throw the first stone we gain no knowledge about whether the act itself is obligatory rather than merely permissible to people free of Original Sin.
Had Christ said 'Stop stoning adulterers. What is wrong with you? This is so not what Ezekiel meant when he prophesied- 'Yea, Israel shall kill in dodgeball so the Greeks can just suck it, Hossanna.'- the meaning would be unequivocal.
Instead, He said 'Let he who is without Sin cast the first stone'. Metaphorically, to say 'throw the first stone' is to actually throw the first stone. Meta-metaphorically it is the opposite.
Which is good because I've tried both Adultery and Dodgeball.
Dodgeball sucks.