And debate is fine and dandy, you can proclaim you opinion but this opinion is not based on reality but on some men's wishful thinking and nothing more. Because most people, especially the reasonable ones and not "activist male agitators" would agree that a woman in this situation has a very reasonable expectation of privacy and no person has the right to interfere with that.
Reason two, his presence might lead to complications during the birth (stress can lead to longer labor and increased risks to both mother and child)
Reason three, SHE DOES NOT WANT HIM THERE. Yes, this is the same reason as reason one but it is the only one that counts, she does not want him there so he has no right or business to be in the delivery room.
And maybe she does not feel safe with him there. Not that I suppose this will be the case here but what if they are married and the baby comes out a different race as the father? That could lead to danger to both mother and child if it becomes clear that the woman has birthed the child of another man.
Also, and I will keep saying this, the woman does not want him there and that is all the reason necessary.