> It's a good thing as it stands today, it is not a good thing for the future of humanity IMO because just one bad action can ruin it for everyone.
Leaving aside the sheer arrogance of thinking you can say with confidence what's going to "ruin the world for everyone," it's very clear to me that any world government that could make judgements like this for everyone would be by definition a tyranny.
Governments do bad things, sometimes backed by popular opinion. You assume a world government would be concerned with global warming or humanitarian issues and would not make bad choices. Why do you assume that? What would stop a world government from committing actual genocide? If it was truly a world government, nothing could stop it.
Hannah Arendt:
> The crimes against human rights, which have become a specialty of totalitarian regimes, can always be justified by the pretext that right is equivalent to being good or useful for the whole in distinction to its parts. A conception of law which identifies what is right with the notion of what is good for—for the individual, or the family, or the people, or the largest number—becomes inevitable once the absolute and transcendent measurements of religion or the law of nature have lost their authority. And this predicament is by no means solved if the unit to which the "good for" applies is as large as mankind itself. For it is quite conceivable, and even within the realm of practical political possibilities, that one fine day a highly organized and mechanized humanity will conclude quite democratically—namely by majority decision—that for humanity as a whole it would be better to liquidate certain parts thereof.