No, it isn't.
First off, you are falsely representing my statement to suit your own debating purposes... but I don't know who you are intending to debate on false premises. But I will get to this soon.
Yes, slavery is the default status quo of the world. Everywhere, in the world there had been nations who have adopted slavery in some form or another, on all continents, on all islands. It was in fact until European countries in the late XVIIIth have decided to abolish slavery that this... form of social strata had begun to be destroyed. Again, this is world wide. There were isolated cases all over the world... maybe even not so isolated, where slavery was modified to be more civil... or rather, less barbaric. But it was Europeans who made it possible for the greatest egalitarian movement in history to happen. No other people could have done it.
But. My statement that if we want slavery we should adopt a global government doesn't mean that we never had slavery before. It just means that if we want to enslave ourselves, deny ourselves our rights and be all subjected to an undemocratic rule of oligarchs, then yes, we should adopt a global government. There has never been one, that is true. But if there will be one, it will be horrible. You, the little person, the small man, will be squashed under the boots of the bureaucracy, the oligarchs and the undemocratic. Granted, slavery will never return to the form it was 200 years ago. As neither will fascism or communism return to the way they were in their "glory days". But there are always new forms of enslavement, of tyranny, and even now, we are subjected to them. All in the name of bigger government.
Also, by "never" I mean during our lifetime (60-100 years). Not really never. Because as Justin Bieber said: never say never
. The last part was my attempt at humor.