The problem in this particular case is that the sensor may be confidently telling you there's something in the way, but in reality it's just a plastic bag. Hard braking at 70mph on a highway as if you were about to hit a concrete wall is probably not a great outcome in this scenario if there's somebody behind you.
If your sensor is confidently telling you that a plastic bag is a concrete wall, maybe you shouldn't be using that sensor to begin with.