I'm not suggesting for a moment that people sympathising with Yuppies Out movement or simply concerned with the gentrification and social cleansing issues are the violent type... But C&F would not know that, and more to the point, it wouldn't be the first time that third parties showed up at an event posted on FB, or at a street demo/ gathering, with ill intentions.
Especially when the event promoted is about targeting a specific business, and the FB page promoting it has less than savoury comments regarding putting bricks through windows or defending Brixton against 'scum'.