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Well, its held on by three round pieces of double-sided foam tape. So I'd try removing the plate, setting it out in the sun to warm up good, then lifting the edges and twisting it a bit. Should come off without too much trouble.
If that doesn't get it I'd try using dental floss or fishing line, running it behind the holder and sawing back and forth to cut through the foam tape. Of course that may leave a messy cleanup.
Be careful with the plate screws if its still got a plate on. Those things are long enough to touch the paint if you give the holder a good push.