Why not just find the porn sites and then find out who has been to them from their records,rather than keep tabs on every place everyone goes.
You've got my vote. My liberal and conservative friends also agree to this.
But honestly, your question is rhetorical.
We
KNOW the reason behind this proposal:
...another step toward total surveillance of citizens, joining warrantless wiretapping, secret scrutiny of library records and unfettered access to e-mail as another power that could be abused.