Uhh, depends on the context.
The parents usually know what they're getting into. So if a child comes of it, he/she needs to be taken care of.
Abortion is something that should be decided on by the parents. I agree with what Oliver said, this is between the parents, and should not involve the government. Buuut, there are instances when the woman should solely decide to have the child or not.
By this reasoning, should men be able to impregnate women without any obligation to staying with the mother and/or fathering the child since they are uninvolved on what goes on in the woman's body? This is where the context thing comes in. Sperm donors do this, and women willingly go through this knowing they're on their own. Again, context - some men are infertile, the woman marries later in life so the child does get a fatherly figure, etc.
And, Relora, I have to disagree with something you said. There are plenty of single mothers out there raising perfectly decent, average children. The man doesn't always get out of the woman's life purposefully.; he could die without first raising his child.
True, dysfunctional families correlate with bad decisions later in life, but not every single-parented child is going to grow up and become a mobster or homicidal maniac.
There are lots of situations the parents and child could be in, it's hard to state my position exactly. We aren't living in a black and white world.