I see this argument a lot.
If you had your way, then child rape would be legal.
If you had your way, then child pornography would be legal.
As if one step would lead to another or if there is even a sliver of nuance, then that automatically means legalizing all the things.
If having sex with kids is harmful, then surely, society would not legalize it simply because they accepted another premise. It is pointless to argue on “if you had your way”, because that would assume that it is intrinsically harmless and that we’re debating on purely moral grounds which serves to distract from the greater issues.
It is also besides a point as that is not what a lot of people argue for and it is so far out of the imaginable for anyone, but presumably those who make this argument, that almost enters the realm of ridiculousness.
And there are certainly some libertarians who would argue for legalizing child pornography on some level, but even this is largely connected to the over-eager prosecution of it.
Banning images even remotely related even beach photos, arresting people for submitting evidence of a crime, being falsely accused of a crime, teenagers being arrested for sexting, banning images of non-existent children, the slippery slope towards more and more scanning and censorship, etc.
This isn’t exactly a shining endorsement of it, but a critique of the way that the justice system handles it. A system that very much should be reformed and shutting down any sort of discussion is not conducive towards any of this.