I used this video as guide to remove my bumper for Execuhitch hitch install yesterday:
https://www.youtube.com/watch?v=9ZWu6uL0abI
At 3:06 they show the clips.

I do see how one of the tabs can pop out. Each tab is held by a couple of plastic pieces. If the bumper moves from side to side even a little, the tab can slide off the first piece on the left, then off piece on the right. There's quite a bit of upward pressure the tab puts on those holding pieces.