What's the problem? I think he will be more popular for doing this, it shows he is not just a PR robot and actually wants to try things for himself. The drug is so wide spread these days that nobody really gives a crap, and our government upgrading it to Class B against all advice just shows how out of touch with reality they are.
I can get hold of weed more easily than I can get hold of paracetamol, and I don't even touch the stuff, so I have not deliberately associated myself with people that smoke it or deal it. I know a guy that lived 5 houses down the street from a police station that had every draw in his bedroom filled with bags of the stuff ready to sell to friends. It's not cool or clever, it's just a fact of life, it's socially accepted and if the governments did their job properly it would be legalised.