Is a world government desirable?

A world government, or global government, is the concept of a single political authority for all humanity. Its feasibility and institutional framework are uncertain, but is it even desirable? Is it the way to lasting peace and global solutions? Or would it lead to a dystopian nightmare?

Pro

 * A world government would allow us to deal with problems that are global in nature, such as global warming, climate change, ocean and air pollution, pandemics and others.
 * There're other ways to deal with such problems that don't require a world government, such as international treatises, free-market, activism, etc.
 * The solutions above have, so far, failed to produce sufficient results.
 * More effective coping with climate, pollution and pandemics.
 * World peace.
 * In exchange for totalitarian government? That's a rather optimistic presumption.
 * A totalitarian government isn't necessary
 * No armies (only police), no weapons of mass destruction (= economic bonus).
 * How would a global authority enforce compliance with whatever policies and laws they intend to impose upon a local population that decides they'd rather do things their way, without harming anyone else? If the answer is "the police", then what makes them any different from a standing army in that case? If compliance is voluntary, then why can't most of these other objectives be accomplished without submitting to a "world government" in addition to such constraints?
 * Free movement of people (no entry permits).
 * Free circulation of goods (no border tax).
 * Rational network of transport (like trans-continental highways and railways).
 * World football superleague above national leagues.

Con

 * A world government would make a world dictatorship possible.
 * A world government would incorporate every political mechanism known to make such dictatorships virtually impossible.
 * An unpopular world government would eventually fall.
 * World dictatorships are possible even without a world government, as has been suggested multiple times by near-global empires such as the British.
 * Even if world dictatorships are possible without world governments, they are more likely when the whole world has one government.
 * A world government is not feasible so we should not pursue or even desire it.
 * Why is it not feasible?
 * The UN becoming world government is unfeasible.
 * World government established in the traditional (imperial) way is feasible and probable, though perhaps not yet foreseeable.
 * Independence and self-determination are impossible if the same government is imposed upon all of humanity.