Here's the rule:
You can remove the obstruction. It doesn't say you have to wait until its your turn, it says you can remove it. That's Rule 15.2a. The flagstick is specifically listed as obstruction in the definition of obstruction.
I actually caught that and thought it was a good post.... - I forgot the smiley face so my reply might have come across poorly. (I was referring to an earlier post in a wry fashion, not so much poking at you. my bad)