Fwiw, I'm not sure any great "explanation" is needed - maybe Class War never used that actual wording, but the spirit of it doesn't feel too far from oldschool CW stuff to me, and I'm sure there's lots of old Class War stuff that would cause frenzied speculation about it being a false flag op if it appeared today. I think some people just hate cops?
Louise Raw's questions in that post seem a bit shitty to me, of all the things you can criticise the UK government for I don't think being too welcoming to refugees and migrants is one of them, and on question 3) "When a woman was nicked for a ‘F*** Boris’ shirt in ‘19, why was he apparently allowed a ‘Kill Cops’ banner?" - surely the problem there is the nicking, not the banner being allowed, and the reason why the cops didn't arrest him for the banner is presumably because they thought they might get people fighting back if they steamed into the middle of the demo?