I'd love to know why you'd vote against having a metro.

Zurich does pretty well with light rail, trams and buses. Public transport is very good there. Two more reasons are that the city isn't that big, so you're in easy walking distance of some sort of connection, and the terrain isn't ideal. A good chunk of the population live up steep hills which are well-served by the tram system. The airport is also very well-connected by bus/tram/rail, and only 10-15 minutes to the centre.

That said, I would have loved to see HBf on this website.

Costs, existing infrastructure and alternatives (S-Bahn was extended) and fears that the local businesses above would loose foot traffic if people are no longer traveling above ground with the trams.

From what I read it was in the 70s in a phase of anti globalisation and growth. Of course in those days car traffic was much lower than now. I bet Zürich residents would be really happy to have had one now. Where I live we have both metro and tram and the metro is so much more efficient due to longer trains, more frequent departures, never being held up by traffic etc.

I really like urban places with public transport on the street. It leads to less cars and more pedestrian friendly streets. Also I think for small distances (Zürich is not that big), I rather ride a bit longer with the tram than going down to a deep metro station, especially in hilly places.

with sufficient density and priority on roads, a tram network might be better, other than having to wait outside in bad weather

The public transport coverage especially with tram in Zürich is already amazing

Because talk radio stations of your city are funded by ads for local car dealers and the show hosts constantly dump on public transportation projects. For example, Quebec City.