The kid going to grow up with no dad and you have no problem with such a selfish act?
I bless the life of the baby and mind my own business about the how and the who.
Yes, it is a sin, but so is a creep going around spreading his seed, or abusing his wife and children, or sitting at a bar drinking his rent.
A good solid family is preferable to this, but this is preferable to a screwed up "straight" family.