I see what you're saying, I think. For consistency's sake, rather than have federal laws we don't enforce due to "policy" (ahem: immigration) we need to set a precedent that a federal law must be enforced or overturned.
Abortion is legal under the Supreme Court. Some states have laws prohibiting or restricting abortion. If you believe that Fed law supersedes state law, then you must also agree that abortion should be legal.
Or to you pick and choose which laws should be governed by the fed or states?
You must know the only way to overturn abortion is through the states?