Not necessary, because the author’s reasoning doesn’t depend on any belief about what would lead nightclubs to be approved. It’s based on a claim concerning what would lead to nightclubs not being approved.

Not necessary, because even if there are slight differences in level of opposition, the level of opposition in each neighborhood can still be sufficient to lead to a city never getting new nightclubs. For example maybe one neighborhood has 100% of people opposing nightclubs, another neighborhood 99% of people, another one 98% of people. That wouldn’t affect the author’s reasoning.

Necessary, because if it were not true — if never getting a new nightclub does NOT automatically constitute something bad for a city — then the example concerning new nightclubs would not guarantee that a city can be harmed by opposition to new development. The author must assume that it’s in a city’s interest to have at least one new nightclub; otherwise, the lack of a new nightclub can’t be certain to harm the city.

Not necessary, because the argument doesn’t concern how people feel about restaurants.

Not necessary, because the author doesn’t have to believe that every new nightclub “invariably” produces benefits. The author just has to believe that having at least one new nightclub in the city would be beneficial. Not every single new nightclub has to bring benefits, but having some new nightclub somewhere in the city would be beneficial — this is all the author must assume concerning nightclub benefits.