Homeless people are far more likely to be victims than aggressors- being homeless doesn’t automatically make you more prone to violence than any other person. Most of the “crimes” they commit are things like loitering, digging through dumpsters for food, or panhandling (where it’s illegal, anyway). If anything, making life harder and more uncomfortable for them by outlawing panhandling, underfunding homeless shelters and taking away places to sit or lie down increases the likelihood that they’ll turn to violent crime. Sanitation is probably an actual issue, but shifting them to another part of town by making all the benches uncomfortable doesn’t solve the problem, it just moves it. Why not provide more places for them to use the bathroom and get cleaned up instead? I doubt most of them want to be dirty.
Helping the homeless by providing them with housing, access to computers and phones, and job resources actually costs about the same (or sometime less) than giving them no aid at all, with the added benefit of getting them off the streets, off of drugs, more sane and healthy, and eventually into a stable, normal life. Unfortunately, I live in America. I don’t know how things are in Japan, but here the sadistic pleasure of watching another person’s suffering is absolutely priceless and people refuse to give it up no matter how much it would benefit society and themselves. The thought of anyone getting anything for free fills them with white-hot murderous rage, and they’d rather see the USA burn to ashes around them than see one homeless person helped back into a stable job, even if it costs them nothing personally.
As for who actually owns the benches and makes the decision to ruin them, I haven’t looked into it, but I’m curious. I don’t know if they’re required to make them fit a certain standard- my guess is that they probably are if it’s a city government-run area like a park, but if it’s a private business they can put up whatever benches they feel like. But I wouldn’t be surprised if the law actually prohibits human-friendly benches entirely in some areas. People really do hate the homeless that much.