Now I've really done it, now I truly understand just how bad things just got. Its difficult to explain so I MS Painted over a photo to illustrate what is going on with the rivnuts.
When you try and remove the rivnut for your spoiler bracket one of three things can happen:
1. Your lucky and the bolt threads out of the rivnut with no issues
2. The rivnut fails to grip the panel it is compressed into, so it just spins with the screw as one piece. You might be able to glue it in place and on a prayer get in removed, or it will lead you to the third and worst fate
3. The your ****ed option. The rivnut is so fused together with the screw that as you twist on the screw you shear off the rivnut at the threads. The bolt is still threaded to the rivnut threads, but now it is completely free and detached from the front part of the rivnut. This means you can't remove the bolt from the hole because it has a giant washer fused on the other side of the sheet metal that prevents it from being pulled out.
If this is on the hatch there is no way to access it from the other side because the hatch is welded together and there is no easy way to reach it. The moral of the story is rivnuts are shitty and you shouldn't play with your spoiler brackets because they are likely impossible to remove non-destructively.