I wouldn't say that at all, in fact I didn't. That is known as a strawman. Make up a comment or idea and attribute it to someone else, and then knock it down.
I said, "Nah, it's not his fault that he grew up with idiots who couldn't speak english."
That means precisely what it says. It wasn't his fault, he grew up with idiots, and they couldn't speak english. None of those things address intelligence as it pertains to language usage.
Additionally, the word "Cuba" has no "R" in it. It is improper to pronounce it with an "R" in it. Also the word "Nah" is a slang usage of the word "no", and is quite acceptable when trying to convey a certain feeling to the writing style of the author.
Now, we can talk about reading comprehension as a possible indication of intelligence. :-)