This thread already exists in H&J. Hell, there are probably several of them.
"If Manchu did not conquer China, Industrial revolution 1700???"
"Chinese army is not 'Squabbling rabble' It is much better trained & Commanded than Roman army, who were a bunch of aristocrats commanded by nobility."
"I've read Roman history and most of the time the German army is just a bunch of guys running forward with axes..... If the Romans had just one crossbow, they would have won many a battle."
Me: "I always thought about moving to Brazil."
Douche: "I thought you said you'd hate to live in America?"
Me: "The US, yeah, not South America."
Douche: "That doesn't make any sense. Brazil's a US state."
Me: "
WHAT THE ****!?"
Douche: "It's true." *pauses* "I thought you were supposed to be smart?"
Me: ...

...
Douche: "Well?"
Me: *ahem* "You do realise that Brazil is in
South America, right?"
Douche: "Yeah."
Me: "South America is not part of the United States."
Douche: *sounding wounded* "Hey, just because it used to be Confederate doesn't mean it's not part of the US again now!"
Me:
*shakes head with utter incredulity* "What the **** man? South America has NEVER been part of the US. It's a different ****ing continent!"
Douche: "Dude, of course it's in the US. It's in
South America."
Me: "No, no it's not. Here, let me try to explain. The US doesn't include Canada or Mexico, correct?"
Douche: "Yeah?"
Me: Well, Canada and Mexico are part of the continent known as North America. The US is also only on this continent. Brazil is in South America, a completely different continent. It is an independent country, like Mexico, Canada, or here in Australia."
Douche: 
"You're ****in' trippin' man. Brazil's in the South. Probably only a few hours from where I live."
Me: *stares at him for a good thirty seconds* "**** it man, I'm not even trying anymore."
*walks away*
The guy in question was a 26 year old man born and raised in Memphis, Tennessee. repeated questioning by my friends, including a hot girl who he didn't know who pretended to like him to discuss this, revealed that he was not screwing with me, but really thought this. To make this even more epic, he had actually holidayed in Argentina.