Not so light a punishment for a recreational user.
My bold, ?
This man chose to operate a revenue flight, while under the influence of an illegal, self selected, non prescribed drug.
He made his bed, he can now lie on it. He knew the rules.
His rehabilitation is another issue, I'd suspect in this case it's for someone other than his employer.
Anything other than zero tolerance would destroy public confidence, and that of the existing workforce.