This is just more meaningless speech-making that demonstrates an unwillingness to consider the question you were asked. That question dealt with unwanted pregnancy due to rape or incest. Your response is tantamount to sanctioning those acts and shows almost total disregard for their victims. In fact, it would be cruel to send thieves to jail if the moral system that sends them there is arbitrary. However, that does not change the point.
All moral systems are arbitrary.
This is easily demonstrated by the fact that different social groupings have different moralities. We have laws which proscribe certain acts since the people who enact such laws have decided which things they want to punish or regulate. Again, any legal system can also be shown to be arbitrary since not all legal jurisdictions have identical laws. Abortion happens to be legal under Federal law, so the people who acting immorally in the eyes of the law are those who wish to restrict or prevent access to abortion clinics or who wish to force their contrary views down women's throats. Also, you are convienently forgetting about the thousands of couples on waiting lists to adopt.