Why is a man who chooses not to be a father a dead beat, but a woman who chooses not to be a mother pro choice?

Because the father is abandoning the baby while the woman is ending a pregnancy before it becomes a baby. If the mother gives birth and abandons her baby she's a dead beat too. 

No man who had a vasectomy at 18 because he knew he never wanted to be a father would ever be called a "deadbeat". 

@Foofa: Clueless. Men can not get a vasectomy at 18 as they won't be able to find a doctor willing to do it. 

Answer: 

A woman that aborts is already a mother. What she decided to do was kill her own child in order to get out of carrying, birthing, and raising her child. 

Deadbeat is a person who is not willing to work, does not behave in a responsible way, and does not fit into ordinary society.

Not a man who chooses not to be a father.

Pro-choice mean  favoring legalized abortion as an option for an unwanted pregnancy.or supportive of a woman's right to choose whether or not to undergo an abortion.or advocating a woman's right to control her own body (especially her right to an induced abortion)

If a woman chooses not to be a mother, it doesn't mean automatically that she is pro-choice.

Your question does not make any sense

You are obviously trying to play word games.

Pro-Choice has nothing to do with deciding if you do or do not want to be a mother.  It has to do with a woman deciding to kill or not kill her unborn child.  

If a man or woman doesn't want to be a father or mother, it is simple.  Just don't have intercourse.  Once you do you are saying that you are willing to accept the chance of becoming a mother/father.