The analogy would be appropriate if the poster compared scooter sharing services with car sharing services. Note that car sharing services are pretty regulated - you can't just dump cars onto the road and create an app. You have to get a permit first.
There's also a difference between people who own their own scooters vs heavily VC funded firms who want to dump as many of their scooters onto the streets as possible to target high growth. An individual owner has the incentive to keep their vehicle off the streets since otherwise people can easily steal them. This is not the same as these large firms, who have GPS trackers on each scooter. Plus, each scooter is so cheaply made that a loss is not majorly important since they have a ton of money in the bank -- each scooter is peanuts compared to the salaries of their software engineers. Individual scooter owners are much more price sensitive and generally tend not to throw their scooter onto the streets.
I think another argument is one of public space. The sidewalk is a public space that I pay taxes to maintain. Why should a low-revenue growth-hacking startup be allowed to use the public space -- which SF citizens pay to maintain -- for free? I'm a pretty staunch capitalist, but this seems like a "privatize the gains, socialize the losses" scenario.
I would be okay if either 1) startups who wanted to deploy scooters faced heavy taxes for certain violations or 2) they proposed concrete plans to explain how they will not clutter sidewalks. The San Francisco government seems to be doing the latter.
TLDR: Incentives are different between individuals and VC funded firms. Also, don't use public spaces to growth-hack your startup. Or if you do, either 1) respect other people who use them or 2) pay fines / more taxes to compensate the city for extra upkeep costs and to compensate other citizens for inconvenience.