Of course a child shouldn't be killed after birth, I'm not migrendel.
If you believe that a fetus is a living person, just like a child who has been born, then your argument about dating would be inconsistent.
If you believe that a fetus is not a living person, unlike a child who has been born, then your argument about dating would be redundant. The mere acceptance of the fact that the fetus is not a person would be sufficient justification for allowing abortion; resorting to a provocative line of reasoning such as "the fact that many men don't date women with kids justifies abortions" is entirely unnecessary.