There are good pro-life arguments and bad pro-life arguments. Yes, that's true, and on a forum, everyone can make their argument, and, if everyone is reasonable, we can all learn something about which arguments are good or bad.
In the "field," so to speak, I believe arguments are usually not much use, except when dealing with those rare individuals who really are seeking the truth.
It is more important, in my mind, to show those you personally can influence, the folly of engaging in those activities and life styles where the question of abortion would ever be a personal issue. Why would a woman want to destroy the very thing her behavior and anatomy is designed to produce for her joy and enjoyment? Why would she want to be in the position of having to consider this?
You see what I mean.
Hank
One think you should remember, though, is that the real audience of an argument is often not the person you are debating with but the non-participating audience. Most fence-sitters seem to read the arguments of both sides instead of posting their own (often confused) opinion. Because of that, it is important to always try to make a sound and level headed arguments that will look good to someone trying to decide which side sounds more reasonable. One of my most satisfying experiences arguing abortion online came when a person that I never heard of before sent me an email telling me that he used to think I was crazy but he started to think my opponents were crazy. That meant he was paying attention and I was doing my job.