Suspecting that they’ll force single family homes out is the issue.
Frankly, unless the population density is already high and geography already constrained so that you can serve a large number of people with minimal infrastructure things like local commuter trains shouldn’t even be considered.
They certainly shouldn’t be developed into the excuse to force higher population density where it doesn’t occur on its own.
I read article the other day, that CA areas are NOT fixing roads because they want people to quit using cars, and them to agree to build more public transportation. That makes zero sense, some autos are necessary for grocery shopping, etc. Bus/trains do not always run convenient schedules.
"Occur on its own" needs to be unpacked a bit. If we allowed the market to rule, many areas in the urban core and inner ring suburbs would shift naturally from single family homes to apartment and condo developments. The demand is there. People are sick and tired of spending four or more hours a day in their cars. I'm not talking about welfare housing here; I'm talking about decent apartments within easy commute range for young professionals and couples. It's zoning that prevents this from happening. Zoning is the antithesis of the market. It's big government planning.
Not that I'm always opposed to it. I live on Capitol Hill in DC. I'm in the historic district. And thank goodness. I'm all for appropriate zoning. But there's a balance to be struck, and placing higher density residential buildings along public transit corridors is generally a good idea. DC is doing this rather systematically along metrorail corridors, and it's a good thing.
Again, this isn't about welfare housing; it's about affordable housing for young professionals and couples, and families with one or two children. People are rebelling against brutal commutes, and we need to rebalance our zoning accordingly. Every city is different. Each will have to seek its own balance. The issue may not be acute in smaller cities, but in New York, LA, DC, Chicago, etc., there is a real need for some serious rebalancing of housing options. That begins by understanding that our larger cities are well past the point of diminishing returns on the automobile commute.
Welfare housing is a different problem entirely. What we've learned from the Pruitt-Igoe/Cabrini Green type projects is that low income housing needs to be dispersed to break up large, self-reinforcing concentrations of people trapped in dysfunctional behaviors. But that's a discussion for another day. Here we're talking about young working people at all income levels who want to avoid spending the majority of their non-work waking hours behind the wheel.