There's a lot of talking past each other on this issue. Sure there's probably clueless people out there, but a lot of left wing housing activists that are skeptical of free market housing liberalization understand very well economics and the benefits of housing supply, but are concerned about the time horizons involved and concrete near term impacts on low income residents.

It is of overall net benefit over the long term to raze a small three story walkup apartment and build something denser, overall increasing the amount of housing.

However, in the short term it's immediately quite (sometimes existentially) bad for affordability if existing affordable housing is destroyed and replaced by brand new (and thus inherently luxury) housing.

So accordingly we naturally see low income housing activists push back against some redevelopment and ask why development is not occurring in wealthy single family home areas where the amount of people impacted is less and class those that are not remarkably negatively impacted.

Personally I think the data shows that in general it is still really beneficial to build out as much housing as possible and avoid the negative impacts of a shortage, but I do think there are people validly pointing at a real problem of displacement.