I agree - this is garbage. Those decals no more interfere with his view than having people in the backseat and the amount their heads would block.
Back windows have never been included in LoS for semi trucks, pick up trucks with campers, among other vehicle arrangements that make the view out of the back window impossible - as long as you still have your side mirrors you are ok.
It is state laws, but I know in Michigan, you could spray paint your back window black if you wanted to. But the front three windows are where the restrictions are (tint %, etc)
