It probably sounded to the SJWs like a tautological argument- especially because they are statists and believe the government is (almost) always right- and thus somethings morality is based on its legality. So to them, they probably thought you werent trying to prevent rape(as in, the crime) but simply classify rape as "non-rape", similar to how in The Wire, cops talk about having to classify robberies as larcenies and the like.
However, given how "rape" has changed in definition so drastically because of SJW and victim-complex ideology, such as when rape is referring to regretful, drunken, or nonconsensual but the girl doesnt explicitly say so, to give a few examples, even the above argument doesnt hold much water. If you label perfectly moral behaviors as rape, it also then shouldnt follow that you should necessarily be punished legally for said behaviors.
However, given how "rape" has changed in definition so drastically because of SJW and victim-complex ideology, such as when rape is referring to regretful, drunken, or nonconsensual but the girl doesnt explicitly say so, to give a few examples, even the above argument doesnt hold much water. If you label perfectly moral behaviors as rape, it also then shouldnt follow that you should necessarily be punished legally for said behaviors.