Earlier quoted context omitted.
His claim was that biological factors "could" explain the gap, at least in part, in that you can't rule out that possibility categorically. I don't recall him claiming that biological factors were the more important factors, never mind the only ones.
If you don't consider evidence you are aware of in an argument, it means you don't think that evidence is necessary to consider. He wants his argument to be considered rigorously in which case it is appropriate to make inferences about what he didn't consider as well as what he did. It's a quiet truth that most disagreements between people have a crucial basis in the implicit nature of how we weigh and consider infor…
So basically, you are saying that you can judge him and what he writes not by what he writes, but whatever you want to arbitrarily insert into his writing.
Even the inquisition had higher standards than that.