There are facts and facts. The OP thinks that Foucault's (pseudo-)philosophy is against the fact that the Earth is non-flat, or that saying that the Earth is non-flat is somehow infused with ideology, but there are also facts that are given to us as true (and which affect the lives of hundreds of millions of people) which are indeed infused with ideology, one of the latest examples being the "fact" that austerity was the thing to do after the 2008-2010 crisis (a "fact" which has recently been debunked by the IMF itself, originally one of its most important ideological backers).
There are facts and facts. The OP thinks that Foucault's (pseudo-)philosophy is against the fact that the Earth is non-flat, or that saying that the Earth is non-flat is somehow infused with ideology, but there are also facts that are given to us as true (and which affect the lives of hundreds of millions of people) which are indeed infused with ideology, one of the latest examples being the "fact" that austerity was the thing to do after the 2008-2010 crisis (a "fact" which has recently been debunked by the IMF itself, originally one of its most important ideological backers).