We shouldn't be spending shit tons of cash to placate irrational fears. What s next?
Who are you to define certain concerns as 'irrational'? A study or two definitely does not establish that.
What s next? Coloured neighborhoods.
In a de-facto manner, such things already exist, so it's little different than what we have.
Often people of the same ethnicity tend to settle together and also aren't necessarily very welcoming of outsiders, either, but the attraction to neighborhoods where people look like yourself is enough to create neighborhoods where different ethnicities are concentrated.
And you definitely do get neighborhoods that are 99% X where X might be White, Asian, Black, etc, and such areas tend to stay that way more or less, and any small minorities tend to concentrate tightly, presumably for mutual support.
Especially where you will have landlords accepting, rejecting, or favoring prospective tenants based on age, Or they might be picking tenants based on criteria without saying as much.
In Tokyo, many, perhaps most neighborhoods and housing units the landlord has a No Gaijin policy.
So realistically, if you are a foreigner, or a person of X descent, then there are certain lists of neighborhoods where you are likely to wind up, and other places that might not be technically off-limits,
but an "outsider" would not be welcome.