There's no argument to be made that an 8 month fetus is not a person. At 8 months' gestation, the baby is viable (able to survive outside the womb), developed, and roughly the size of a newborn. All of the arguments against personhood fall apart, and, unless they want to make a bizarre argument based on location, the abortion advocate has to simply concede the point.

When discussing abortion, I routinely can get the pro-abort to admit that an 8 month fetus is a person. What they will NEVER admit, however, is that it is murder to kill an 8 month fetus.

The logic is unbelievably straightforward.
Killing innocent people is murder
8 month fetuses are people
8 month fetuses are innocent.
Therefore, killing 8 month fetuses is murder. The conclusion must follow from the premises.
But they never admit it. Why? Because, almost always, support for abortion has nothing to do with rights, logic, or morality. They have an emotional attachment to the issue that defies all logic. And since liberals typically define religion in terms of an emotionally-driven belief that defies all logic.....

Liberals really should stop trying to legislate their religion on other people. That's theocracy!