you think that is bad...i was putting a baby changing table in that back last week, I rested it against the bumper so i could pick up the legs and pivot it in. Keep in mind this is just one of those flimsy light tables. The pivot rubbed off the paint down to the ABS plastic in a small 1" section where the spine of the table was. Another one happened at the tail light. The dealership replaced the rear taillight that had a bad seal...they must have used a screw driver to pry it off and that rubbed of about an inch of paint to the ABS plastic (didn't notice this till a few weeks ago)
My other car has plastic bumpers and I have loaded stuff the same way...you may get a little scratching from the move which i will handle with some scratch remover, but I have never seen the clear/paint come of from such little force.