Lindsay over at Majikthise has done an excellent job of distilling the talking points we on the left should be using around this whole "Culture of Life" vs "Culture of Death" thing that is evolving around the tragedy of Terri Shiavo.
It boils down to valuing reason over emotion and recognizing that there are practical limits to everything. We can make positive changes to our world but we have to reasonably measure the effects of our actions and put our limited energy to work where it will do the most good. It means taking the emotion out of the process and replacing it with reason and compassion.