Well good for you, but as someone who lives in the centre of Amsterdam I can understand the motivation to discourage drug tourism.
Edit: to clarify it's not the reams of tourists getting high in coffee shops that I have a problem with, but the knock-on effects of it. Tourists treat the city like an adult themepark and recently the city council have been taking steps to address these problems.
I was in Amsterdam this morning and everyone I talked to explicitly mentioned it being done against drunk Englishmen on stag dos. I remember myself hating fractious drunk English stag parties, and have fond memories of pointing polite and hapless stoned Italians to the street we were already on.
Tourists from the UK are reviled by Amsterdam and they’ve ruined it so much the entire city centre now has an alcohol ban.
It has nothing to do with weed.
Also, Dutch stag parties seem not to be that far off what happens in the UK.