Whether you view it as an ethical win or a practical one, reducing homelessness helps all of us.
Or if I live in a people-that-didn't-just-get-a-million-dollars-go-instantly-homeless-with-their-entire-family community, this is another big win for me. What a boon to the economy, and man we all just dodged a massive bullet.
Like, if you're worried about the inflation shock that would create, then the same people who have the power to give a million dollars to everyone but me would certainly have the power to raise interest rates and take other measures to prevent the sudden mass availability of wealth from wrecking havoc on the economy. But that's a separate topic, and if I'm affected negatively by this, I'd be upset at the powers that be for failing to mitigate the negative consequences of their actions. I wouldn't be upset at all at the hundreds of millions of people who are suddenly wealthy.
That is how it harms people. Even worse, it harms only the most responsible people.