You are defending the rhetoric of a genocide perpetrator. It's like saying "what if Hitler was right about the Jews? I don't agree with his tactics, but that doesn't mean there wasn't a problem."
I think another way of saying phrasing the same idea. Let us assume that Muslims are intentionally having as many kids as they can to become a demographic majority in the future. How does that affect how we should act?
The above phrasing I count as very different from defending rhetoric of a genocide perpetrator because the answer to the above question is not "Kill all Muslims".
What I don't understand is why are you arguing your position? What do you propose I do with respect to the acquisition and spread of knowledge?
Even if Muslims have higher fertility rates than Buddhists, the observation is meaningless.