"Don't use oil" is not a ridiculous statement. There's this little thing called trains. They're actually a heck lot more efficient when they don't use oil. The only thing they don't do is make suburban commuting convenient. But I'm guessing that if it comes down to a choice between giving up the suburbs and starving to death people will decide they like living in cities.
You can't put trains everywhere. Blaming the suburbs for the usage of cars is such a stereotypical thing to do I don't even want to address it, but since you brought it up: Cars are used in cities plenty and mass transportation as opposed to private transportation isn't a solution because it does not address the actual issue: energy. What we require is energy sufficient to transport people where they need to go to gather the resources they need for their personal subsistence. Gasoline engines provide that for most people right now, but they'll need to be replaced.
And as before, oil is necessary for
a lot of things, not just gasoline.
If you think that we are in danger of mass starvation then I recommend you try looking at the price of meat sometime. It takes a lot more farmland to feed people meat then it does to feed them vegetarian foods. If we were on the verge of a collapse of food production then meat would start getting much much more expensive. (Non-meat food would get expensive more slowly because so much of the cost is packaging and handling.) But we don't see that. Meat is becoming a larger part of diets worldwide and we have things like YUM foods investing billions of dollars in KFC joints in emerging markets. This is the same YUM foods mind you that is owned by Berkshire Hathaway, an investment company that recently bought the largest freight train company in the US.
We still have oil to match our consumption, so the spread of meat is definitely not a valid metric. Come back when we can extract less oil than we need to consume and I'll accept that argument.
We are very much in danger of mass starvation if the oil isn't sufficient.