Your slavery analogy is flawed. The argument is that only women have a right to have an opinion about abortion because only women have abortions. So by the same reasoning, only rich white people have a right to have an opinion about slavery, because only rich white people owned slaves.
Black people were the VICTIMS of slavery, and thus are comparable to the unborn child in any such analogy. I don't hear any feminists saying that only unborn children have a right to an opinion about abortion.