"Cars are great to go between cities fast, but inside cities they should behave like guests"

No, especially in north american cities where you can walk few places, cares are another form of transit, like anything else.

Relatively few people actually ride bikes.

"Pedestrians, cyclists and public transportation are the most efficient mode of transportation inside a city" this is completely false in most situations, especially in North America.

You cannot reasonably walk 5Km to work every day and back. The vast majority of people live far from work.

Even with cities that have good public transit, it's not optimal in tons of cases.

Cars - or things like them - are going to stay. They are not going away.