Then you're wasting your own time too, and also costing the government more money.
They're actually paid by billable hours, so if you spend an hour explaining why you're not cooperating they get paid for it; however, if you end up not cooperating you do end up hurting the census worker's productivity per hour; I don't see why someone would deliberately want to do that to someone just doing their job.
If you don't want to cooperate, simply don't open the door to them or answer their calls.
When people call to sell me something I always say "OK, let me go and get my wallet", and then I just put the phone down and go about my business. I enjoy ruining their per hour productive. If they didn't want it ruined, they shouldn't have called me.