Gender is NOT a social construct

According to the dictionary, gender is synonymous with sex. Sex is not a social construct.

Begging The Question

Circular reasoning. Dictionaries don't give words their meaning, they barely try to capture it. Moreover Oxford dictionary reads "The term is also used more broadly to denote a range of identities that do not correspond to established ideas of male and female."

Positive discrimination of disadvantaged groups in employment and education is immoral

Discrimination is immoral when it results in the inferior candidate being selected. Positive discrimination on a variable that predicts performance is needed for the best candidate to be selected. Best individually does not mean best for the team.

Begging The Question

Even if you accept the article as conclusive research, it talks about advantages of diversity in general, not the kind of diversity you get based on discrimination by race or gender (disadvantaged groups). You basically assuming your initial point that race/gender based discrimination will result in better team without proving it.

Positive discrimination of disadvantaged groups in employment and education is immoral

Discrimination is immoral when it results in the inferior candidate being selected. Positive discrimination on a variable that predicts performance is needed for the best candidate to be selected. Best individually does not mean best for the team.

Irrelevant Conclusion

Results do not justifie means. Just because discrimination may offer advantages to the company it does not make it less immoral to the discriminated individual. The immorality is even more pronounced in the case of a public school discriminating against applicants.

Positive discrimination of disadvantaged groups in employment and education is immoral

employment or work in general may not be a zero sum game. If there is intrinsic value in diversity, a diverse team may perform better than the sum of its parts.

Fallacy Of Red Herring

Straw-man fallacy. While it is true that "work in general may not be a zero sum game" and "there is intrinsic value in diversity" the previous premise specifically addresses a situation that is a zero-sum game. Further, the fact that diverse team may perform better is irrelevant to the (im)morality of negative discrimination.