I agree to a point. It is mitigation, not a defence. He deserves less of a punishment than some big time charlie doing it in night club toilets. But it is not a reason to escape punishment, you can't create a precedent whereby personal sadness is an excuse for this.
The one that springs to mind with cocaine is Mutu. He was fired the following month and got a 7 month ban
Coke gets sniffed because of the huge amount of alcohol you can tolerate while on it. Enough alcohol to poison yourself. It's not about winding down, it's about blotting out (which the booze does, not the coke).