I think that should be the decision of the man. I'm against abortion, but this is not even related. He's preventing the need for abortions by preventing his sperm from impregnating someone.
Actually, if someone is going to be having sex but has no intention of ever having children, I think a vasectomy is much more moral than the abortion that comes when he accidentally gets someone pregnant.
EDIT:
It is my belief that a fetus is a life, so I act according to that belief. A potential for life and an actual life are drastically different.
My daughter has the potential for an A in math. So, should I act as if she has it and reward her accordingly? Or should I wait to act until that potential turns into an actuality?
For LDS, the reason we are against abortion is because we do not know when the spirit enters the fetus. But we do know the spirit is not present before conception, so there is no need to protect sperm.
If we felt that potential was the same as actual, we'd be having a funeral and big hoopla everytime a woman had period. Because, *gasp* she murdered that potential for a baby by not getting pregnant. But that's not how we act, because we don't believe potential is the same as actual.
Yes, miscarriages happen. In that case, a life has died. Just like when a baby, child, teenager or adult dies. Tell the woman that experiences a miscarriage of a wanted child that it's not a big deal because it's not a child, it was just a potential. I'm willing to bet you'll walk away from that conversation w/ a bloody nose. Every woman I've known that miscarried a wanted child has gone through a mourning period just as she would for a child out of the womb.