How to remove side curtain airbag retainers on 2014?

I've got the headliner down and I am trying to figure out how to the remove the hardware. Looks like the red insert spreads the retainer, so it most likely needs to be removed first. Tried numerous times to remove the red insert, but I'm having no luck.

Any suggestions?
These were a pain to remove! Took like 2 hours to get them all out. Bent a finishing nail at 45 degrees about 1/2" from the tip and took a grinder to make it a standard screwdriver. Used it on top from the outside through the hole and a small standard screwdriver from the bottom and pressed the tabs on the insert toward the middle. Slowly worked the insert out all of the way. Once removed, I found that by placing the small standard screwdriver into a groove in each tab of the retainer, it can be easily removed. The insert is the hard part, the rest is cake!