I'd think they're wrong. And I'd spend my time explaining why.
But I wouldn't take their opinion personally; I wouldn't be upset by it; I wouldn't feel compelled to question their intelligence, morals, ethics, or motives. I wouldn't complain that they're being unfair, chauvinistic, or sheltered.
Because it's not a sincere question asked in good faith. It's just another attempt to evade addressing anything I actually say in favor of insulting my intelligence.
No, I don't speak other languages fluently. I speak some Spanish and a little French, and I can cuss you out in Japanese. But English is the only language I speak fluently. And if you were half as sincere as you no doubt are going to claim to be, you'd have realized that I NEVER SAID I AGREED WITH THEM. I only pointed out that they find THEMSELVES lacking.
I answered the OP's question honestly and accurately to the best of my knowledge, understanding, and perceptions. Which is WAY more than you or any other respondent has done.
So, go ahead. Mock me for only speaking gasp one language! It doesn't make me wrong.
I read it 10+ years ago. As I recall, its main point had to do with differences between Old World and New World populations.
Since Africa falls into the Old World along with Europe, I don't think the book actually supports any conclusions about this topic.