Not sure how spoofing matters.
In the case of the two blissey shaving, that wasn't a spoofer - they were there.
Also, spoofers generally won't put their new pokemon at the bottom of the gym, so you can't shave them out without taking out most of the gym... There is no real way to target anyone specific in Pokemon Go without hurting everyone else at the gym, and that really is the way it should be...