Do you understand the difference between private property which you control (your own house) and private property which is open to the public (bars, restaurants, 7/11s, shopping centres, etc)?
The article states: "consuming cannabis in public spaces is a major taboo, enforced with the risk of fines or imprisonment." A bar may be private property, however it is a public space.
From your assurance that you only consume cannabis "if the bar has no customers", does that mean you immediately stop when a second customer arrives?
Following your logic I will start a similar practice. After having ten beers I will only drive on roads with no other vehicles.