All true. But the problem is that you assume everybody is a weak-minded idiot, and that legalization will lead to universal addiction. This is simply not the case, and has never BEEN the case. Drug over-users are a tiny fraction of the population even where usage is completely legal.
These sources have data for the Netherlands:
http://www.drugwarfacts.org/cms/node/67
http://www.ukcia.org/research/DutchPolicyAndCrimeStatistics.html
From what I see, it looks like legalization would be a good thing.
The Netherlands has a population of 16.7 million and is socialist.