h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

>>Would this have happened if he had chosen the hookah (or a hooker) as his recreational drug?

There is a school of thought which suggests it's not physical drug you use which matters, but how you believe it will affect you.

"Social anthropologist Kate Fox argues that we need to re-learn much of what we think we know about the effects of alcohol.
Alcohol does not make us disinhibited, violent or anti-social, she says."
http://www.bbc.co.uk/programmes/b015p86z#synopsis

Whether there is any truth in her assertions or not, the 'cultural construct' attributed to the use of cannabis is that it makes the user laid back, lazy, etc.

So that MP would still (most likely) have behaved very differently if he had consumed the contents of a couple of bowls instead.

Yes, I agree.
However, it is still interesting to investigate the sorts of claims she makes, and consider how suggestible we are when it comes to altering our conciousness. For example, I know some people who use NLP-style 'anchoring' to bring about drug-states when they are straight.