I have an analogy I use sometimes.

Imagine you're walking down a sidewalk and somebody throws me off a building and I land on you. You are injured, but you also broke my fall and saved my life, for which I am grateful. Now who should be punished for your injury, me, or the person who threw me off the building?

That is an analogy for non-consensual procreation. The person who threw me off the building should be punished for what happened to both of us, and you should not be held responsible for caring for me while I heal from my injuries. But I also shouldn't be euthanized. 

For a consensual act of conception, you have to imagine by some twist of logic that you were one of the two people who threw my off the building as well as the person I landed on. Now you are culpable for what happened and responsible for my well-being.