Federal funding of abortion clinics is justified because of what they provide. In addition to providing abortions, these clinics also often supply birth control and other health services to those who could otherwise not afford them. In addition to this, I find that a women should have the option to get an abortion if she feels she is not ready to have a child, and without federal funding her ability to do that might be more limited.
Abortions should NEVER be funded by the government. First of all that would be the government interfering with a woman and her right to choose, but I guess it's okay to the pro-choices if governmenting is footing the pill. Second, there are other places women can go for birth control such as the health department. The health department will do it on a sliding fee based on income. Third, there is the option of adoption. Fourth, have the guy wear a condom. If he can't afford one, maybe the woman should raise her standards, or not have sex. If a woman wants an abortion, she should have to come up with all the money herself. My tax dollars should not have to pay to kill an innocent child because someone didn't plan ahead. I don't mind helping low income people get birth control, but I should not have to pay for abortion.