Fair enough, I've just had enough close calls with campus police (true story) peeling out into parking lots and then charging down sidewalks while people are still walking down them in order to chase down someone that was biking while intoxicated.
While his argument does leave some room to dispute whether or not he would have considered driving home as opposed to longboarding/walking, I don't think it is open enough to just say "well, he was longboarding, so he might as well have been driving". That's just as stupid as extrapolating that just because someone smokes cigarettes means that they might choose a more dangerous form of smoking (i.e. smoking weed, smoking crack etc.) just because they were smoking something.
I agree that police are essential to maintaining civil order (in most instances at least) and the safety and well-being of others, I just think that there are better things to do than patrol around Helsinki's "calmest area" when actual crimes are being committed every minute.