There is respect for a family for their loss, but there should also be respect for the dead. You're right, what if he did not want to father a child? I find it bizarre and sick to do this after his death. Just shows the importance for everyone to make a will expressing both wishes before and after ones death.
Why not use the father's sperm? They could have donated his sperm to some woman of child-bearing age. Would have been much less twisted in my opinion.