In what way is it broken? Is it still possible to thread the original cap screw you used to do the installation back into the nutsert? If so, one fellow posted that after threading the capscrew back into the nutsert, he used a hammer, tapping on the head of the capscrew to collapse the legs of the nutsert, which then allowed him to pull the nutsert back out of the hole in the tailgate. Other than this, I think you would have to carefully grind the lip of of the nutsert and push it into the tailgate. You could then recover it through the access port on the tailgate.
It is smashed, I know it's a little hard to see in the picture but the treads are no longer in a circle it's more of an oval now.