I "chose" to leave the tailgate on my Dodge with the AF camper, considering the maiden voyage was from WA to AK for a year and I didn't have a convienent way to haul the tailgate. Was a little concerned since even with the bed mat, the tailgate sat a little higher than the bed, so the camper was definately bearing on the tailgate.
After 5000mi or so hauling the camper with the tailgate on, including a lot of dirt/off/rough roads, only evidence of the camper on the tailgate is a couple dents on the inside where the camper "settled" in.
Road rash rock chips is not an issue at all. Doesn't happen. I've put 10s of thousands of miles hauling stuff with the tailgate down with no road debris damage. A lot of it in the winter with sanded roads and plenty of gravel roads.
I've set 4000lb pallets of grout on tailgates.
I'm not saying any of this is within the rated capacity of a tailgate but I'm confident that the little camper on your 1/2 ton won't hurt it.