I think the parent was referring to: homelessness on the rise, lower-income residents being forced out, the need for many service workers to transport themselves to the city because they can't afford to live here anymore, housing speculation and foreign investment leaving units empty and driving up prices, etc. All of that "changes the character of the city", IMO for the worse. One reason (of many) for these changes is obstructionist behavior toward building housing and increasing density.
At least that's what I'd be referring to if I were to make the parent's argument.
You'd think it wouldn't take so much effort to defend the claim "if you build enough housing, people won't be homeless", but it does. So let's go with a prominent example: Tokyo.
Neighborhoods in Tokyo have no local control over zoning, and houses are widely understood to be a depreciating asset, not an investment. So Tokyo builds enough housing and homeowners can't pull up the ladder behind them.
The homelessness rate in Tokyo is astonishingly low and decreasing: just 1600 people in a metropolis of 13.6 million. Almost everybody can afford to live somewhere, because there is enough housing for everybody to live somewhere.
You may think I'm saying that your neighborhood has to look like the Ginza area, and I'm not saying that at all. Tokyo contains some calm, beautiful, residential-focused cities such as Setagaya. (If this is confusing: a metropolis can contain a city.)
Japan culture is very different than US. There is inherent respect obtained from having a job, any job, and dedicated yourself to it no matter how small. Being without a job or worse, homeless, brings much shame to that person and their family. There is strong social pressure to maintain your career and pour many many hours into it.
There's strong social pressure to maintain your career and pour many hours into it in the US, too.
That doesn't have very much to do with whether there are enough places to live. If the places where the careers are have fewer available places to live than they have people, it doesn't matter how dedicated you are, you can still fall out the bottom of the market.
Correct me if I'm wrong, but it sounds like you're implying that homeless people in the US are homeless because they aren't ashamed enough of their situation to work harder and find a job, any job. That's... a gross misunderstanding of the problem, if so.
I think Tokyo is a good counter to the nonsense perpetuated in SF that the law of supply and demand doesn’t somehow apply to housing.
Homelessness however is more a multi-headed beast, and Japanese culture likely plays as much into a lack of people on the street as does housing availability.
At least that's what I'd be referring to if I were to make the parent's argument.