Any dealer (licensed or private sale) that won't remove the zip tie won't sell a gun to me.
The question is at what point should the dealer remove the zip-tie for someone looking at a gun? Ask yourself, what percentage of the guns you touch at a gun show you actually end up purchasing?
I am extremely conservative about touching guns at gun shows. I generally won't touch anything, even when offered, unless I am seriously considering purchasing it. And, even then, I only purchase a fraction of the guns I handle. My thought is that vendors should be wary about letting just anyone work the action on their guns.