Historically Japan would have executed someone like this and that's not an exaggeration there have been examples in the past. Now is that too authoritarian? maybe .
But Johnny Somali (apparently he's Ethiopian by the way so he even lied about that and his real name is Ramsey Khalid Ismael and he really hates people knowing that for some reason so im putting it out there. ) being a public nuisance , disturbing the public constantly and insulting the country constantly and yet nothing can be done about it because he's technically not breaking the law.
Now imagine tons and tons of people behaving like Johnny Somalis/Ramsey Khalid Ismael and creating public chaos and nothing can be done about it cause they are technically not breaking the law.
Suddenly authoritarianism makes more sense
You're mixing up democracy with law and the structure of current governments and culture. What you're critiquing sounds more like today's "Liberal Democracy", but that's a fake, ever-shifting set of standards you can never pin down. In reality you could have an authoritarian junta that lets criminals run rampant to punish segments of the population, or a "democratic collective" that lynches whoever the will of the people decides should be killed for any reason.
Democracy makes democracy look bad enough all on its own, but this is more the Japanese being too "nice", trusting, and rule oriented, while Japan is a puppet of the United States. I also agree with current_horror's comment about the multicultural cause of the problems, and why authoritarianism eventually ends up being the solution to breach of trust.
Reminder that Japan once had a samurai class that exemplified and enforced codes of honor in public.