Um, this law is wholly illiberal, why would liberals ever want this?
"But why would they want to kill their own customers?"
"Why do madmen do anything? They're bloody madmen, that's why!" -Arcanum
Political debate gets a lot easier when you pretend your opponents do not have any motives besides being card carrying villains. This also has the added benefits of not needing to think your own politics or their consequences, after all since your opponent is evil you are by definition good. Operation Barbarossa? What's that?
Basically, the OP was simply confirming their tribal identity as one of the Good Guys, and happened to belong to the tribe called "conservatives". Since the issue at hand is not one of the flag issues - issues used for defining the tribe's identity - they were free to acknowledge the proposal as evil and attribute it to the other tribe ("liberals"). Had this been one of those issues, for example gay rights, we'd been treated to a convoluted logic to "prove" that their tribe was correct and the other evil.
This kind of behaviour is typical for political fringes, where it serves to help the members keep their flame going, but since the US only has two parties it gets injected straight to the core of the nation's political life, the result being increasing instability.