A football coach objects to his team playing against a team with a female player because certain of his players’ religious beliefs preclude them from hitting/tackling a girl.
I have never heard that argument offered, have you? What an interesting proposition. I wonder if this will go to court.
I can't say that it's really my area of expertise, but Title IX is a well-tested statute. It has been either affirmed or expanded in a number of different SCOTUS rulings.
So long as their isn't a female team in the same sport, girls have the constitutional right to play on the boys team, and the team has to make reasonable accommodation for showering/lockering areas - that's it, so says the Supreme Court.
The coach is positing a creative defense, but it's not going anywhere, IMHO.