For all the dumb things Selena Gomez has been doing lately (pissing off her neighbors with late night parties, all things Justin Bieber, etc), this one is definitely a HUGE checkmark in the GOOD MOVE column.

For some reason, there's some "fan" who has been wishing cancer on Selena on her Instagram pics. FINALLY, Selena was all like...oh HELLLLLLLL no and commented back on a pic from the user laying the smackdown in the most polite way possible.

(Now, I actually tried to go to the Instagram of the "fan" to post the comment, but since Selena's verbal Knockout punch, the girl deleted her profile. But you can see a screenshot of Selena's comment to the girl HERE!!!