I nominate this for stupidest thread of the century if you really think this will be a logical discussion and not a flamewar.
It's actually very simple. Without getting into my opinions on the subject, those that support legal abortions do not consider a zygote/fetus to be a human, and therefore, it is not murder.
Also, are you seriously dumb enough to think it's a "cut and dry case"? Have you ever watched a political debate?
edit: also, why is your point of reference suicide? Most people would go to murder as being a more apt comparison since abortion is much more akin to killing another person than yourself. I get the whole "right to choose/its my body why can't I have an abortion or kill myself" thing you're going for, but wow. I stand by my first statement (dumbest thread of the century).